My guess is she's probably just one of those people who likes to treat her friends like crap so she feels better about herself and only wants to be friends with people who will let her. When you're young you just like hanging out with someone who has similar interests, and you don't necessarily realize their personality flaws. But now that you're older you can see that she is not a good person.

I know this isn't what you want to hear, but you really need to just let her go. You can remember the positive things about your friendship and the fond memories you two had, but know that she's no longer that person. I've had this happen to me with my former best friend and I cried about it for a while, but I felt such a huge relief once I realized that I didn't need the anger and stress that came with having her in my life. We had some great times together and I think about it fondly, but my life is 100% drama-free without her and that's the way I want it.