You can’t possibly understand why she refuses to have sex and that ‘s because you aren’t a mind reader. The fact that she has had sex before but refuses to have sex anymore tells me that she’s suffered some kind of trauma. Either she’s been abused, raped, abandoned after giving herself, or perhaps she got pregnant and had an abortion. The possibilities are endless.I have the impression that she resists talking to you because doing so would open up all the feelings that she is trying to keep buried. By avoiding sex and any talk of it she is engaged in the ostrich policy (pretending that ‘it’ will all go away by hiding her head in the sand). The problem is that the ostrich policy is sending you away.You need to tell her that you have the sense that something terrible happened to her in the area of sex. Tell her that you understand that she is avoiding any contact in order to protect herself from a rush of bad feelings and memories that would come up if she had sexual contact. Tell her that the problem with this coping mechanism is that she is driving you away from her.Ask her if this is what she wants to do. She will surely say no. Then tell her that if she wants to keep you and have a relationship that she needs to stop hiding. Insist that she begin therapy right away. Offer to go with her to a therapist, if that will help. If she prefers, she can go alone.The message she needs to get is that you won’t allow her avoidance defense to destroy your relationship. The push that she gets from you is the push she needs to get past her denial.Let me know what happens.