What to do with a friend who isn't acting like one?

I can relate to you. I'm going through the same thing myself. As of late, I've stayed her friend. I'd do the same if I were you. She may not be acting like a true friend now, but she'll get over it. This happens in every friendship, no matter how strong. Be her friend, stay a good friend. She'll take a good look at herself one day and know she wasn't right to do what she's doing. Hope I helped!