How do I deal with a good friend I can't stand anymore?

I went overseas with this girl and came back absolutely detesting her. It's been 7 months and It is too late to say anything about the situation and she thinks we have become better friends, which is strange because I avoid seeing her. She also has the tendency to treat me badly in front of other people, but I don't want to completely cut ties because we have mutual friends who don't know about the situation....what do i do?