My 'friends' are lying backstabbing 2faced jerks. What do I do?

I've been tight with a bunch of girls for about 4 years now. There's 7 of us in the group. I started hanging out with a few other people and they had gotten really angry & jealous and wanted me to come back to them as if they own me. Ever since then things haven't been going well. They take every joke i say to them to offence & find ways to twist my words and make me look bad. The other day I was at my mates house & I knew something was up because nobody had been talking to me properly so I went through her messages (I know this wasn't right but I had to find out what happened) and 5 of them had a whole conversation on Facebook & how i had said a few things i remember not saying. (Twisting my words) & then one of the girls who appears as if she's the 'group leader' said some really offending things about me.. She always manages to turn everyone against me. So then i checked the date of these messages which was 2 days ago & i remember talking to the one of the girls on the same day i checked the messages and she was talking to me like nothing had happened. They also have a nasty codename for me which is find is really childish. I know the obvious thing to do is leave them but out of the 7, 2 of them are understand and real nice girls.. that's about it. Should i say something straight to their face or just forget it and leave them ?