In "Ladybug & Cat Noir (Origins - Part 1)", she was one of the new students in Miss Bustier's class.
In "Stoneheart (Origins - Part 2)", Mylène watched from afar as many students crowd Ivan after his previous akumatization. Later, as she was rushing to class, she bumps into Ivan, who attempts to sing her a song he wrote, only for his loud voice to scare her off. When Ivan gets akumatized into Stoneheart, Mylène winds up captured by him along with Chloe and taken to the Eiffel Tower. She was eventually freed after Ladybug deakumatizes him and was amazed by her Miraculous Ladybug. Ladybug then shows her the lyrics of Ivan's song, which she finds beautiful. Ivan apologizes for scaring her earlier and promises to be more gentle, to which Mylène hugs him in response.
In "The Bubbler", Mylène was one of the many people Bubbler forced to attend Adrien's surprise birthday party. Though she dances at the party, she was just as miserable as everyone else. When Ladybug and Cat Noir arrive, Mylène and the others cheer for them, angering Bubbler and prompting him to trap her and everyone else in floating bubbles, though she was later freed after Bubbler's defeat.
In "Mr. Pigeon", she heard of the derby hat competition their school was hosting and was in the courtyard walking with Nino.
In "Timebreaker", Mylène and the others cheer for Alix as she and Kim raced. When Alix was akumatized into Timebreaker after her watch gets broken, Mylène was one of the many people she causes to disappear from existence, though she was brought back after Timebreaker's defeat.
In "Copycat", she was seen in Ms. Bustier's class with her friends.
In "Lady Wifi, Mylene was in class until it was interrupted by Lady Wifi and she left the school.
In "The Evillustrator", Mylene was in Science class and was paired up with a classmate for a school project.
In "Dark Cupid", Mylène was listening to Ms. Bustier's literature lesson about love and after class was over she received an embarrassing photo of Kim from Chloe.
In "Horrificator", Mylène played the leading role in a short film Miss Bustier's class was working on, but she constantly got scared of the monster mask Ivan wore. When Chloé made fun of Mylène's tendency to get easily frightened, she bursts into tears and ran out the classroom. Ivan attempts to cheer her up by giving her a pin from his favorite band, but Mylène believes that she wasn't right for the lead role and went to the bathroom, where she wonders out loud why she's so easily scared all the time. Her emotions become negative enough that she is akumatized by Hawk Moth into Horrificator, a slimy monster who grows bigger the more people are afraid of it. Horrificator captures several students in the school and traps them in slimy cocoons, all while feeding on their fear. However, she was eventually defeated by Ladybug, Cat Noir, and several of the non-captured students that helped the duo. Once deakumatized, Mylène shared a kiss with Ivan.
In "Darkblade", she heard that elections for class representative were happening and was happy that Marinette chose to run against Chloe. When Mylene heard that Jagged Stone was signing autographs at City Hall she rushed over to get one. However, she expressed fear when Darkblade and his nights tried to break in but she was comforted by Ivan.
In "The Mime", Mylène and her father Fred went to Marinette's house to retrieve the hat Marinette was fixing for the latter. She expressed pride at the fact that her father will be playing the leading role in The Mime's Extraordinary Adventures and was flattered when he says that he keeps a photo of her in his hat for good luck. Later, she spends a little time with Marinette and Alya before leaving with the latter. When Alya wants to show Mylène a video she had recorded earlier but can't find her phone, Mylène calls Marinette and asks her if she has Alya's phone.
In "Princess Fragrance",
In "Reflekta", Mylène was shown sitting in the front row for the class photo. Later, after Reflekta's defeat, she joins her friends in the park to take several group photos together.
In "Antibug", when Chloé complains about someone pulling her hair, Ms. Mendeleiev glared at Mylène. She denied doing anything, which Chloé confirms to be true.
In "Despair Bear", Mylène watched Tom Dupain's cooking lesson with the rest of her classmates until it is interrupted by the fire alarm going off. When Mr. Damocles punishes the whole school as a result, Mylène sweeps floors and angrily glares at Chloé, knowing that she's most likely the one who called the fire department in the first place. Later at Marinette's house, she helps Marinette by modeling a hat she designed until she receives an invite to a party from Chloé. At first she believes that someone hacked her phone, but then concludes that Chloé wanted to say sorry for earlier and suggests that maybe deep down, she is nice. While at Chloé's party, Mylène approaches Chloé and asks her where the ice cubes are, to which Chloé rudely tells her to get herself and makes fun of her sweater. Shocked, Mylène is nearly akumatized, but she calms down when Chloé takes back her comment and gets the ice cubes for her. She slow dances with Ivan at the party, and after Despair Bear's defeat, bakes macarons at Tom Dupain's cooking lesson, though she bursts into tears after Chloé makes fun of them.
In "Befana", Mylène attends Marinette's birthday party and gives her a fashion book as a gift. When Befana arrives attempting to turn Marinette into coal, Marinette dodges the shot and it hits Mylène instead, turning her into a coal statue. She is later returned to normal after Befana's defeat and continues celebrating Marinette's birthday.
In "Robostus", she was in Science class with her friends and becomes amazed at Max's robot friend Markov.
In "Gigantitan", Mylène along with Juleka, Rose, and Alix are called by Marinette and Alya to a meeting at Marinette’s. When Alya reveals that she has a big scoop, the girls first think that Alya knows who Ladybug is, but when Alya says that Marinette has a crush on someone, the girls reveal that they already know it’s Adrien, with Mylène pointing out how obvious it is. Mylène agrees to help set Marinette on a romantic date with Adrien, commenting on how she can always be counted on. As part of the plan, Mylène is given the codename “Sunflower” and is put in charge of alerting Officer Roger of Adrien’s bodyguard’s illegal parking after Juleka puts a fake NO PARKING sign by his car. But the mission goes awry and as a result, baby August is akumatized into Gigantitan. When Gigantitan grabs Ladybug and nearly puts her in his mouth, Mylène and the girls help Ladybug by distracting Gigantitan with a giant sign that looks like a lollipop. After Gigantitan’s defeat, Mylène and the others reunite with Marinette and then watch her failed attempt at asking Adrien on a rickshaw ride. Once Adrien leaves, Mylène shares a rickshaw ride with her friends.
In "Glaciator", Mylène goes with Ivan, Nino, Alya, and Marinette to get ice cream at André’s. She shares an ice cream with Ivan, but the night is cut short when Marinette, heartbroken over Adrien not being able to come, sadly rejects the ice cream André tries to give her and walks away.
In "Gorizilla”, Mylène goes with Alya, Rose, and Juleka to the swimming pool, and the four girls wait for Marinette to arrive. While waiting, she and the others are kept entertained by multiple photos posted online of Marinette with Adrien.
In "Captain Hardrock", Mylène helped Kitty Section set up their equipment on the Couffaine houseboat for the music festival. When the band does a soundcheck, Mylène gives everyone earplugs, commenting on how they’d need them. She then witnesses a confrontation between Anarka and Officer Roger over the volume of their music and is as shocked as everyone else on board when Anarka is akumatized into Captain Hardrock. When everyone refuses to play music for the supervillain, Captain Hardrock chains everyone up and throws them below deck, with Mylène being chained against Ivan. She is later freed by Ladybug and, after Captain Hardrock’s defeat and Officer Roger’s approval of the music volume, watches Kitty Section perform.
In "Frightningale”, Mylène went with Marinette, Alya, Rose, Juleka, and Alix to audition as extras in Clara Nightingale’s music video. When Marinette is offered the role of Ladybug, Mylène is happy for her, though when Marinette turns down the offer to be with her friends, Mylène hugs her and playfully calls her crazy. However, when Marinette changes her minds after Clara almost gives Chloé the role of Ladybug, Mylène cheers her friend on but is disappointed when Chloé causes the shoot to be canceled. When Clara is akumatized into Frightningale as a result, Mylène finds a safe place to hide. After Frightningale’s defeat, Mylène participates in a new version of Clara’s video and watches it with her classmates, commenting on how everyone gets to be in it.
In "Zombizou", for Miss Bustier’s birthday, Mylène explains that her gift is a braid of hair inspired by the breathing classes that help her to be less scared of akumas. She appears disappointed upon learning that Chloé didn’t get Miss Bustier anything but is indignant when she later learns that Chloé sabotaged Marinette’s gift. When Zombizou bursts into the classroom, Mylène is surprised and runs away with the rest of her classmates when Ladybug begins fighting the supervillain. However, Sabrina, who had been infected by Zombizou, kisses her, she turns into a kissing zombie. After Zombizou’s defeat, she is returned to normal and shares a kiss with Ivan.
In "Frozer", after Marinette explains her dilemma with Adrien and Kagami, Mylène offers up the excuse of having to finish an essay on Periwinkle’s migration in order for her to get out of it. However, she is surprised when Marinette reveals that she’d rather not cancel. When Marinette expresses her belief that she and Adrien may be better off as just friends, Mylène and the other girls disagree and quickly get into an argument.
In "Style Queen (Queen's Battle - Part 1)", Mylène was seen in the front row of Gabriel Agreste’s fashion show.
In "Queen Wasp (Queen's Battle - Part 2)", Mylène is seen in the front row of Gabriel Agreste’s fashion show.
In "Reverser", Mylène was seen alongside Ivan and several other protesters fighting against Mayor Bourgeois’ space dumpster program. However, she was horrified when Reverser showed up and made it so that the mayor sends all the dump back into Paris.
In "Malediktator”, Mylène and her classmates laugh when Chloé presents a video of herself dressed as Queen Bee to the class for a school assignment. Later, when Chloé announces that she was leaving Paris, like many other students and staff, Mylène is delighted at the news and celebrates. However, the party is soon crashed by Malediktator, who makes it so that Mylène and several other people at the school begin destroying the building. After Malediktator’s defeat, Mylène attends a party honoring Queen Bee.
In "Catalyst (Heroes' Day - Part 1)", like most of her classmates, Mylène believes Lila when she says on a video chat that she’s in the country of Prince Ali and will be meeting with him to get his approval on a pollution-reduction project for Heroes Day. Mylène then listens as Mr. Damocles praises Ladybug and Cat Noir’s heroism. When Miss Bustier asks her students what they'll be doing for Heroes Day, Mylène is excited when Marinette claims to be organizing a macaron tasting with many delicious treats for the whole school. However, Mylène is devastated upon learning that an akumatized Ladybug destroyed Cat Noir with his own Cataclysm (unaware that it was an illusion created by Volpina). When a bunch of scarlet akumas swarm the school, one of them turns Mylène back into Horrificator then follows the other akumatized villains to the Eiffel Tower.
In "Mayura (Heroes' Day - Part 2)", Horrificator and the other akumatized villains praised Scarlet Moth until he signals for them to stop. She then fought the French Miraculous superhero team, but after Scarlet Moth is reverted back into Hawk Moth, she was returned to normal. Later, she attends a picnic in honor of Marinette and all her good deeds.
In "Chameleon", like most of her classmates, Mylène believes Lila’s lie about having tinnitus and needing a front row seat, so she changes seats so that she sits next to Ivan. When Marinette complains about having to sit in the back and supposedly upsets Lila, Mylène and the other students glare at her, forcing her into the back. Later at lunch, Mylène believes Lila when she claims to have a sprained wrist and can’t carry her own tray, so she and several of her other classmates bring her food for her. When Marinette reveals that Lila’s wrist isn’t sprained by throwing a napkin at her and making her catch it with the “sprained” wrist, Mylène is momentarily shocked, but when Lila claims that she’d wanted to catch the napkin before it hit Max’s eye, Mylène buys it and angrily asks Marinette if she’s proud of herself. After the defeat of Chameleon, Mylène gathers with her classmates as Lila continues to lie about her friendship with Ladybug. Back in class, when Lila claims to no longer need a front row seat due to Ladybug curing her tinnitus, Mylène and the others decide to go back to their original seats.
In "Animaestro", she along with Ivan had their eyes closed in an effort to help Ladybug and Cat Noir defeat Animaestro.
In "Backwarder”, Mylène and the other girls are called for an emergency meeting at Marinette’s house, though because it is so early in the morning, they were exhausted. When Marinette reveals that Adrien is going to the royal wedding in England with Kagami and asks the girls how to prevent a potentially romantic weekend between the two, Mylène suggests that they organize a demonstration to make the trains go on strike, though Alya points out that they’d likely just take a private jet or helicopter. The girls all agree that the best way would be for Marinette to just tell Adrien how she feels. At school the next day, Mylène and the others ask Marinette how everything went. Marinette tells them that she wrote him a note, and Mylène and the others cheered for her. When Adrien approaches Marinette, Mylène was ecstatic but even more delighted when he gave Marinette something. However, she was perplexed upon discovering that it’s constipation capsules.
In "Gamer 2.0", she was one of several people taken prison by Gamer 2.0 until Ladybug and Cat Noir defeated the titular villain setting her free.
In "Oblivio", after Alya and Nino explain that they were akumatized because they’d been embarrassed at being caught playing Super Penguino, Mylène says that everyone loves that game.
In "Party Crasher", she was planting trees at the Seine with her friends.
In "Ladybug", Mylene was in class when she heard that Marinette was accused of stealing the test answers to the Mock Exams. She was shocked aware that like the rest of her that Marinette would never cheat.
In "Cat Blanc"
In "Miracle Queen"