Okay so awhile back I was cheated on by my boyfriend and another girl I've always had a problem with, and so has my best friend, well call her R. I repeatedly have stuck up for R against the girl, well call her K. K decided she wanted to fuck my boyfriend, then blame it on her being drunk. R has always had problems with k, with her making tumors and bullying her. I have never liked k but she has never messed with me until the whole cheating thing.  I asked r if she could stay the night tonight and she told me she wasn't able to. Come to find out, she went to the beach with her boyfriend and k. She has does this kind of thing so many times. She'll have problems with someone and talk shit about them , and then go and be friends with them. I have been friends with her since I was 5. I am furious that she has betrayed me once again. I have no clue what to do.