How should I make this person in my novel?

I am writing a book and I want this person in my book to be more of a popular kind of stuck up person (teenager), to stress the idea of overcoming many different boundaries. I don't want her to be SUPER stuck up, because she has to be nice and cooperative with the other people she is working with. I don't want her to be that stuck up because people don't change within and hour. She has to be not so far apart from cooperative, but she still has to be stuck up. What kind of thing s would that girl do without being too nice or too stuck up? Also some backround on her is that she lives with an Aunt who really doesn't have time for her, so she does the stuck up thing to feel wanted.