Wow! First off her behaviour is understandable. Having trouble saying no is not uncommon with people who have PTSD and like was said before I strongly recommend she sees a therapist. That would help with some of the pain and confusion. Also maybe she needs to reevaluate the relationship with her boyfriend and see if she wants it to be a sexual one in nature. It sounds like that not what she needs from him.
You mention that she isn't attracted to her boyfriend. I'm wondering if she's gay. Whatever is happening she needs to see a professional about this. All anyone on this site can do is give ideas and support; a lot of which is based on past experiences.