What should I do? Confused?

I have three enemies at school..2 of them used to be my best friends the 3rd just kind of tag alongs with them..My ex-best friends names are Jenn and Nikolina and there friend is Sarah..I have a friend named Tiffany and she's friends with them and she promised me she wouldn't tell them what we talked about. Couple weeks ago, someone hacked on Tiffanys yahoo and e-mailed all of her friends horrible, immature things except Jenn and Nikolina..Tiffany doesn't want to think it's Jenn because they're friends and Tiffany does tell them everything I say..I don't know if I should still be friends with Tiffany or what I should do? She says she wants to be friends with both of us but, that's not going to work..I don't know what to do? Help?!