I need some advice with friendship bullshit

Hi,

So basically one of my super bestest friends had an issue with me being closer to another friend, she broke down and told me she'd kill herself if I left her (she was super drunk). Anyway after that we had a mature conversation and I told her that I'm always there for her, because I am. Well a few months after that my best friend and this other girl, who I'll call Bitchtits, got together and planned to tell my friend to leave me alone and vice versa for bitchtits' friend. They completely denied it happening but we all know they planned it together. This whole thing sprouted into a huge fight and she ended up not talking to me or my friend for literally most of the school year. She had an issue with one of Bitchtits' friends and they were bulling her and photoshopping pictures of her and I told her, behind my best friend's back and I didn't tell her I did that. Fast forward to now, my best friend found out I told my friend about the picture and is now blaming me for disregarding her feelings and saying she couldn't talk to me about the problems she had with our friendship because I kept telling her that she was imagining things. I feel really hurt that she'd believe that because I've never done anything like that to her and this school year, I was essentially replaced by bitchtits. I don't know what to do, she's been my friend for 7 years. I don't trust her anymore because of what she does behind people's backs and I don't have the guts to tell her that. I feel like she is trying to manipulate this already fucked situation and will not take my answer. I would be glad for any advice, thanks.

Also, sorry for the long and confusing post