OP, I think why she doesn't want to have sex anymore is because she wants more from the relationship. I had a similar thing going on with a girl where all we did was fvck. Every time I would see her that's all I wanted to do, and that's all we did. Until one day, she asked me "What are we?" and I came up with some BS. Then after that she didn't wanna fvck so I was bit angry, but I played it off well and I didn't contact her that much after. Then later she called and said that she was sorry that she didn't want to fvck and to not be mad at her and I told her I wasn't mad, and I played it off really well. But it could also have been that she was on her rag, which she did mention one time.