My friend and I are drifting apart. I'm not sure what to do?

[Marykate]

We are in high school and we've been friends for 3 1/2 years now. It's been me, her, and two other girls since the beginning. She is the kind of person that chooses a new best friend every 2 months or so, and currently has one outside of the 4 of us, that's fine. She acts drunk as soon as she's had a drop of beer( I know everyone has a different tolerance to alcohol but I'm talking about one sip and shes acting like a fool), so I told her to calm down and stop acting like shes drunk because it's not fun for everyone else and she yelled at me and said " well what do you know". So now, we don't really talk and she's written sarcastic things about our friend group on twitter, one was about me. She tweets that we are never there for her, but she's never there for us either, I've been having trouble with someone in school that everyone knows about and she hasn't even tried to console me or comfort me. Can I do anything to mend the friendship or should I not be friends with her anymore?