I know you are hurt, and anger makes it so much easier by blaming them, but try to be the bigger person and politely tell her to leave you alone right now. Let your ego rile you up a bit on the fact that she's goin over to this guy's house and having some new exciting sex while coming back to you and subjecting you to her feelings of resentment. That's ****ed up and isn't a sign of love (although I don't think she intends to do this like that). If she keeps trying to contact you, keep reminding her that you want to be on your own and that she should respect that. Considering she has options and is certainly taking advantage of them, shutting down one avenue will certainly add to her desperation factor. But that's not the point. The point is you need to be on your own to get yourself back to normal. Which won't be easy, considering your attachment to her and the fact that she's going to continue to pop up in your life because she can sense the weakness on your part. You have to do this for you and as you have noticed, the more times you have seen her, the worst it's gotten. Do yourself both a favor.
Waking up next to a beautiful girl,
Step outside and say hello to my beautiful world.