Friend Problem?

I am having a friend problem, I have gone to my 'rents about this and I have talked to friends teachers etc. Here is the problem. My one friend doesn't like my other friend. (CONFUSING RIGHT!!! :) LOL) She has told me stuff saying that she did this and that. I believe her because I've seen it. I want to tell her that I don't want to be her friend. I did. But then, we end up being friends again and it keeps repeating over and over again! Please help, I wanna get this situation over with before conflict gets involved. We almost got into a hee-uge fight. I had to be held back. Then, we ended up being friends agian! MAN! I DON'T KNOW WHAT TO DO! Feel free to answer me........soon :- (