I Need Some Help

Well one of my best friends recently broke up with her boyfriend. And her boyfriend is one of my good friends too. Well her story is that she told him she was breaking up with him because someone told her he liked another girl (or something like that). His story is that she said I told her he liked another girl (or something like that) and we were all talking on the phone, and they were trying to get me to choose who I believed. I told them I wasn't picking sides in any of it. Well anyway she ended up hanging up on us. And I was talking to her on the internet and she says that I said that I believed him, which I didn't, I'm 100% sure, because I'd never choose between them. And well now she is mad at me and won't talk to me, she signed off, and I don't know what to do. She thinks I picked him over her, even though I told her that I wasn't going to pick over and over again... I don't know what to do... I know this is confusing and may seem pointless but does anyone have any help for me? (And if you find this, then I'm sorry but I don't know what to do, I'm trying to explain it as fairly as I can...)

But he's my friend to, and he told her that he was joking, but then he told me he just said that to keep her happy... I really don't want to loose her as a friend...

I have, she knows she's one of my best friends, and I'd never do that to her...but she won't believe me and I don't know what else to say...