Though I was never a good example of the woman I will describe here there is a part of my that understands her. Generally it will be because of the woman that sex is not taking place. There can be any number of reasons that it begins, but generally speaking I think it is a realization of her situation in life. If she is not in the place in life that she imagined, a woman can become rather depressed and rather than deal with it will withdraw into herself. For most women sex is a very emotional thing. It feels great, but that wash of dopamine is just too much for the girls that mix up lust and desire for love. Even if that is not the case, a woman can have herself convinced that it is in no time, blaming her partner for her misery. Once she begins to see her partner as an enemy, even a slight enemy, it is difficult to have sex with that person. It would just not feel right to her as if she is going to have sex she wants it in this romanticized love thing. After a while, a woman gets used to not having sex and if she masturbates really doesn't need anyone else to get her off. After a while she can convince herself of this as well. Once it becomes apparent that he isn't going to just grab her and take her, which is really what most women want their partner to do, she just sort of becomes accustomed to how things are and works to keep them that way. She is likely comfortable in her misery. Now, there is a frightening look into the psychology of women for ya.