Mis,
There are a lot of good things about her. You've got some good basic structure to her, but I do have a few questions. Please help unconfused me.
I am a bit confused about likes and dislikes since they're all sort of lumped together. Can you clarify that for me?
Also, the whole robotic limb thing is a bit of a problem in the magical world. That sort of science would most likely be considered a muggle concept since they could enchant a prosthesis to do robotic sorts of motions and actions. Not sure it works in the Rowlings world. I know it would mean a significant redesign for Estella, but you might want to consider having her be interested in developing a better magical prosthesis.
I'd like to see more about what her relationship is with her parents and how she got them to allow her to go to Hogwarts instead of Durmstrang. Viktor seems as he would be pretty dedicated to his old school, and while Eli had already earned some celebrity status as an artist (which no doubt was part of Viktor's feeling like Eli could handle being farther away from home), Estella doesn't have that. How did she get her parents to allow her to go to a different school than their traditional choice for a wizarding school?
And--I see no mention of her having any love or interest in magical creatures or animals. Where did the choice to become a beast specialist come from for her? It feels to me as though its a bit disconnected from her desire to develop this artificial limb--or however you work it out to fit into the wizarding world.
Let Eli or me know if you need help.