Background
Amanda O'Neill was born in America. Due to political drawbacks related to magic, Amanda was forced to attend Luna Nova by her family, who sought to secure a job through her. She was obviously not happy with this idea that it eventually affected her integrity as a student of Luna Nova later on, and became the school's rebellious student. In fact, at some point prior to the Enchanted Parade movie, she was found guilty of breaking and entering; attempting to steal from Luna Nova. While there, she became roommates with Jasminka Antonenko and Constanze Amalie von Braunschbank Albrechtsberger. She has also exhibited an interest in athletics and dancing, as she's shown to be extremely agile.
The Enchanted Parade
When professor Finnelan explains who the other problematic girls are beside Akko, Lotte and Sucy, Amanda is the first student introduced, stating she dodged security obstacles and tried to steal from the academy.
Later, when the girls meet to plan the parade in the room of the protagonists, Amanda proposes that Akko learns the broom dance and the choreography that they could do at the parade, however, this is unsuccessful.
While shopping for preparations for the parade, Amanda, Jasminka, Constanze and Akko are involved in a quarrel between local children. This eventually results in Amanda losing faith in Akko's ideas for the parade, leaving Akko to single-handedly solve the issue.
When Akko solves all the problems of the parade by herself, she invites Amanda and her other friends to participate in her performance. Amanda, Constanze and Jasminka watch Akko lift the final pieces of the parade boat and they help her complete the preparations. Amanda also accompanies Akko to contain magical energy from the Sorcerer's Stone within the Shiny Rod to ensure the plan works.
Amanda places the Shiny Rod on the parade boat and congratulates Akko for making it work as planned. She then gives the orders to start the parade, but Akko decides to continue waiting for Lotte and Sucy despite having passed the meeting time. Due to an unexpected accident, the fireworks are activated and Amanda and the girls are forced to start the parade after attracting the audience.
The local children again start trouble by stealing the Shiny Rod during the performance; Amanda and Akko pursuing them. After having rescued Thomas, Amanda escapes on her broom quickly through various obstacles and moving monsterous objects until she is trapped by magic, and throws herself into the parade boat, thus passing the Shiny Rod to Akko and Sucy.
After Akko, Lotte and Sucy defeat the Titan, the three are led by Amanda, Jasminka, and Constanze respectively to greet and announce the closing of the parade to the public. Amanda again participates this time using her magic wand in the last war of magic and tomatoes against Thomas and his friends.
TV Series
Don't Stop Me Now
She was reintroduced in the 3rd episode of the show. She is first seen doing broom acrobatics during Broom Flying Class and is reprimanded by Professor Nelson for flying dangerously. Later in the episode, she manages to steal the legendary Shooting Star broom and plans to use it during the Luna Nova Cup. This backfires due to the broom's defiant nature, it manages to escape Amanda's grasp and flies out from the Relay Point in the top of New Moon Tower. After Jasminka supposedly gives Amanda the baton (a ring), she manages to catch up to the Shooting Star broom and sees Akko controlling it. As Amanda tries to take the broom from Akko, Amanda is disqualified as she was actually handed a donut rather than the ring, and thus failed her baton pass.
Luna Nova and the White Dragon
She appears again in the 5th episode when she and Akko along with their own roommates were in charge of manually doing the school laundry after she and Akko started an argument during class. While doing their time, she and Akko notices a flock of dragons stealing the Sorcerer's Stone. Using Constanze's reserve magic fuel, the six of them follow the dragons to retrieve the stone. The skirmish ended in a failure, resulting Lotte, Sucy, Constanze, and Jasminka getting captured. Amanda and Akko decide to infiltrate the dragons' lair but get caught by Fafnir. As Akko tried to convince Fafnir to return the stone, Diana and the Luna Nova faculty enter and Diana calls out Fafnir's lies regarding the school's debt. Due to the efforts of the six being fruitless this time around, they are once again back to doing the school laundry. Then Amanda and Akko get into another argument over who is better suited as Diana's rival.
Orange Submariner
She makes a minor appearance during the 7th episode when she was evaluated during Broom Flying. Although she successfully completed the test course, she was given a C- due to her recklessness. During their lunch break, Akko comments about her D-, with Amanda replying that she was surprised that Akko even managed to get a grade since Akko cannot fly a broom at all. Akko then talks about Amanda's dexterity with the broom and ask Amanda if she ever wondered of becoming a broom dancer. Amanda stated that she just lives in the moment and doesn't wonder about the future. She then invited Akko and her roommates to sneak out to a party, but Akko declines, saying that she needed to study for exams. Confused about Akko's newly-emerged studious behavior, Amanda asks Sucy if she gave Akko some weird mushrooms.
What You Will
During the assignment of tasks for the Samhain Festival, Amanda ends up choosing the fairy that gives her, Constanze and Jasminka the task of being the cleaners of the waste, to their very displeasure. When everyone meets in Akko's room to discuss the festival, Amanda expresses her lack of interest in being the Monlit Witch as well as her distrust of Akko being able to do so since she can not fly on a broom.
Samhain Magic
During the Samhain Festival, Amanda, Constanze and Jasminka do their task, finding a fun way to do it. Amanda cleans up the waste using skates and a scooter. She then encourages Akko during her presentation.
New Age Magic
At the beginning of the new semester in Luna Nova, Amanda meets with her friends in the garden of Luna Nova, discussing about the new teacher that will arrive at the school. Amanda asks Akko to show the magic that she used at the Samhain Festival, but she explains that she can not use the Shiny Rod at any time, leading to reveal the events of how he found it in the Arcturus Forest, revealing a possible mystery around it.
Amanda O'Neill and the Holy Grail
Amanda is "bored to death" at Luna Nova and sick of the rules, work, and punishments. In the close open she swears to Akko that she will finally leave the school tomorrow, and she "means it this time". She decides to go investigate a rumor that the Holy Grail is located at Appleton Academy, a prestigious school with over a thousand years of history, where it is used in a traditional ceremony. Akko thinks the school might be related to the fifth Word, which Ursula informed her is related to tradition and history. Resolving any doubts Akko had about leaving when Ursula was coming back in a moment, Amanda forcibly guides her out the door. Appleton Academy is famous for their hatred of witches dating back to medieval times. It is Amanda's plan to go into the academy in disguise as a (male) student, but Akko, fearful of being discovered, does not feel particularly reassured by Amanda's promise to take all the blame if they get caught so she's the only one who gets expelled. After spotting Andrew Hambridge, Akko makes up her mind and disguises herself as a mouse, traveling in Amanda's pocket. When Amanda comes across the Chairman's son Louis Blackwell, she acts aggressively and nearly gets them into trouble. Andrew saves them from Blackwell's suspicions that they are witches, but Akko remains upset that Amanda endangered the mission so thoughtlessly. Amanda says she doesn't care at all about the Words. She tells Akko that she just came to go out of Luna Nova with a bang, which strikes Akko as very selfish. She can do what she wants, and proving it she leaves Akko, still a mouse, on her own with Andrew.
Amanda goes to watch Blackwell and other students play cards, and is amused by his cheating, exposing the cards he hid under his sleeves to friends. She says that if he's going to cheat, he should learn from the best, and does a card trick where she makes a whole deck "disappear". This angers Blackwell, and as he gets up to confront her she pulls out her wand and begins to cast an object modification spell. However, she left the Ley Line Router with Akko, and her spell fails, but she has revealed herself to be a witch in front of everyone. Blackwell summons a squad of inquisitors, who capture her.
Meanwhile, Akko has found what she believes to be the Holy Grail, and realizing that Amanda has been caught, she goes to "save" her, easily getting captured herself. They are again saved by Andrew, who proposes that they settle the matter in the traditional way, a fencing dual between the knight statues. If he wins, he will break the cup and punish the witches. While Louis's proficiency with the sword is superior, Amanda was able to win due to her exceptional acrobatic skills (and without magic, since she does not have the router). Blackwell destroys the cup anyway, releasing Croix's magitronic device, which possesses a suit of armor that seals itself around him. In the ensuing duel Andrew throws Amanda the router and she combines her wand with the (by then badly damaged) foil, creating a magic sword with which she is able to defeat the suit of armor. When Blackwell's father arrives and demands explanation for the damage caused to the school grounds, Andrew saves them once more. The young witches take off and go back to Luna Nova, and for once Amanda feels guilty about all the trouble she has caused. Akko asks Amanda to stay at Luna Nova so they can have more exciting adventures together.
Sky War Stanship
Amanda attempts to try and get Akko to leave Constanze alone, knowing that she would rather Akko not help her. Later, she goes to cheer her and Constanze on at the Wild Hunt.
Yesterday
She makes appearances during the 23rd episode when Diana headed to Akko's dorm room and found that the friends of Akko were there. Diana explained to everyone about Akko's condition. While Amanda believed that Akko might want to leave Luna Nova, Lotte called her out, refusing to believe Akko would do that and Amanda taking back what she just said. Together, Diana rallied them to find the missing girl but to no avail as every place they went to was a dead end. Later after their searching, Amanda and the others arrived at the shop and found Akko at the table with Diana. Near the end, the owner free of charge offered them drinks.
The Road to Arcturus
While returning through the Ley Line, this one suddenly dissapears, causing Amanda and the others to fall in the Arcturus Forest. Amanda tries to use her broom to leave, but all magic energy in the area have been absorbed by the Noir Rod. The girls then goes where Chariot and Croix have been attacked by the Noir Rod in a giant dragon form, and sees how Akko manages to save them and unlock the last Word of Arcturus.
Tree of Leaves
As the Noir Rod possess a missile and lauch itself to destroy the nearby county, Akko insist that they must stop it. Amanda is skeptical that they are capable of it, but finally decides to believe in the words Akko. After uniting all their brooms and receiving protective suits from Chariot and Croix, the seven young witches fly to the Noir Rod. Amanda is the third to leave, giving a strong boost to Akko and the others.