I car pooled with a women who told me that she could go the rest of her life without sex. She said this while she and her husband were divorcing. She was about 30 years old at the time.
It's probably hard for men to understand, because as I understand it, even "bad" sex for men is rarely physically painful. Imagine that every week, you had to go get your penis rubbed raw and didn't get to orgasm, and you were supposed to act enthusiastic about it.
When my ex-husband and I were divorcing, I also felt like I would be happy to never have sex again- because during our marriage, I had come to associate sex with physical pain. Maybe he thought I was cutting him off, but he was hurting me and didn't see fit to change that.
Now that I've been in a good relationship for almost two years, we have sex several times a week and it's great. If she doesn't want the sex, maybe you're doing it wrong.