Wat should i do?

You shouldn't have to choose only one best friend, they're both your best friends. But talk to the new girl that hangs out with you guys, ask her if she knows why you and your friends are fighting, tell her it all started when she came in. I know, easier said then done. If she lies and says, i don't know what you are talking about, then say, O i think you do. then walk away and DON'T be her friend. Tell your two friends to stop being frinds with the new girl, because it causes all of you guys to fight. Tell them whats been happening, and hopefully they will understand and you guys will make the right decision.