@THEMOSTRANDOMESTSTAY I suggest confronting her the next time she treats you badly. Like if she says something nasty, tell her straight up you don't like it. This works well if you don't want to cause unnecessary drama because you aren't in the wrong. It also shows her you're setting boundaries and won't put up with her crap.
I did this with a few people once I kind of found my voice and shown them I'm not a pushover, now they treat me really well.
But I understand if you'd rather want to cut her off because sheesh, people am I right?
You don't have to be friends with her at all, just slowly remove yourself and your friends from her life and if she asks about it, tell her the truth.