Huge Fight With Bestfriend, HELP PLZ!!!?

Im going to high school next year and I'm a girl. Ok, so my bestfriend is actually not very nice to me. In fact she is mean and bossy. She is also very nosy and needs to know every single detail of what happens to me. It's also either her way or no way. For example, if she wanted to go downstairs and I didn't want to she would literally drag me down. No joke. And she has made me cry before, not in front of her but like when I'm home and thinking about the stuff she said to me. But she can be very nice as well, and she is a good friend in other aspects. She always stands up for me and helps me with watever i need. My other friends always ask me, 'why do you hang out with her?' "Shes so mean and you're so nice." "She's so mean to you.' Etc... When I first met her there were four of us and she was nice to me. Now there's only me and her and she's a lot meaner. Anyways, she told me that someone told her that I talked behind her back and she believes it and she's mad at me now. I didn't talk behind her back, except for agreeing with my friends when they say that she's mean and that's the truth. In a way I think she deserves it but she just texted me saying do you wanna talk about it. I haven't talked to her about it tried to avoid her. This happened today. i don't know what to do. I kinda want to talk about it but don't really know what to say. I don't really want her as my bestfriend anymore and a lot of people don't like her. I mean sure as a friend, but not a bestfriend. But i don't know how to really stop being her bestfriend. I mean we eat lunch together with the same group and hang out with most of the same people. So I don't know what to do. Help me please!!!! Any advice is welcomed. Thank you! 10 pts