Your W was sexually assaulted sometime in her life. I have dealt with the same issue and have a very similar story.
Does your W imply that there is a secret from her past? Is there a time in her life or event in her life that she does not want to discuss? That might be a clue.
There is a lot of attention paid to childhood sexual abuse from parents. However, a lot sexual abuse or sexual assault is perpetrated by peers in school. For example, she might have been at a party in high school, and some guy got her drunk and raped her. Girls that have experiences like this have some of the same symptoms as people who were sexually abused as a young child by a parent. Quite often, the survivor blames herself. "I shouldn't have been there", "my H will think I am a dirty slut if I share this with him", "I should have fought back", are common feelings.
I would encourage her to share her first sexual experience that she can remember. Unfortunately, she may not want to share because the experience might have been painful. She may also resent you for bringing up painful memories.
One word of advice: do NOT try conventional therapy. It does not work for sexual assault survivors. The fact that your W has gone to multiple rounds of therapy without results is a major sign that prior sexual abuse is a cause of the problem.
Here is a great article on the internet that describes the best way to go about therapy for survivors of sexual abuse.
