I've realized that my protagonist is very similar to a character in another book. I'm not really sure how to change her so that she is different, especially since she has been in my head for a long time, and everything about her (personality, appearance, etc.) seems to be set. It feels weird changing anything about her, but I feel as though I have to, now that I see how similar she is to the other character. Any advice on how to go about doing that?