Eva is just an ordinary girl living in California in the United States. She's a huge fan of the Subdigitals and is excited to have backstage access to their next concert. But when given a DVD, Eva unwittingly opens a file and falls under X.A.N.A.'s spell, who was using the band's fanbase to spread over the Internet again. Unlike most possessed people, her eyes show no sign of X.A.N.A.'s symbol, removing any physical signs of possession.
Eva forgets everything and becomes unaware of X.A.N.A.'s actions in her body. She becomes determined to go to France and to Kadic, where the Lyoko Warriors are. Her mission? Gain their trust, join them, and kill them.
She makes it to Kadic as a transfer student, not able to speak very fluent French. Within a few days she has mastered the language, surprising everyone. She makes good friends with Aelita and Odd instantly falls in love, eagerly trying to get to know her. She lives in an empty house in town, lying to everyone that she is staying with relatives. She begins to realize that carrying out the final part of her mission isn't going to be too easy, especially with her blossoming friendship with Aelita, but she doesn't give up.
One day, Odd comes over to her house to ask her out. He's sadly disappointed when he realizes that she is in fact being controlled by X.A.N.A., and he is possessed in turn. The two then never leave each other's side, constantly holding hands and pretending to be a couple.
X.A.N.A. then uses Odd's key position in the group to infiltrate Franz Hopper's original version of Lyoko, the Sandbox, located in the Hermitage. Meanwhile, Eva, Ulrich and Jeremie are captured by the terrorist group the Green Phoenix and taken to Lyoko, Eva appearing dressed in Subdigitals clothing. Achieving its goal of reaching the virtual world, X.A.N.A. releases the two kids.
Eva becomes conscious in the virtual world, not knowing anything that happened since she opened the file. She is a little confused about Ulrich and Jeremie, their clothing and language (she finds she can speak French without having learned it), but very happy about her own clothing. She simply sits back and enjoys the scenery in the virtual world while Ulrich and Jeremie work out what to do next.
Later on, she fights alongside the Lyoko Warriors and the Men in Black against the Green Phoenix. Her attack on Lyoko is discovered to be a loud scream that emits multicolored musical notes from her mouth that are powerful enough to deflect Yumi's fans.
When everything is over, Eva goes back to the United States to find her father, a lawyer, has filed a complaint against Mr. Delmas for harboring a missing child. Granted a scholarship by the head of the Men in Black at Jeremie's request, she then returns to Kadic soon after to continue her schooling with her new friends.