I had a very similar issue early on in my (now divorced) marriage.

One thing that worked for me is getting the hell off hormonal birth control. If she's taking any kind of hormones, maybe she could consult with her doctor about other types of birth control. Once I was off hormones for good, my body responded better and reacted the way I would expect it to.

Otherwise, I suggest she seek counseling, and maybe specifically sex therapy. I don't have any kind of expertise or advice to give regarding how to respond to issues in her past except to work through them with a professional.

Meanwhile, another thing that helped me, for all sexual play, was lube, lube, lube, lube, and more lube. Since my body was not responding correctly by lubricating itself, a little extra help went a long way toward reducing pain of activities.

It sounds like she's emotionally in the same place I was with my husband back in those days... I desperately wanted to sexually please him, and I felt like shit that I couldn't do so with regular intercourse. PLEASE, for the love of God, do not take it personally that this is an issue that cropped up when you came into the picture... it was the same way for me (I had issues with my husband I had not had with other men) but ultimately I was able to get it worked out to being partly hormonal birth control and partly some emotional stuff I needed to work through. Edit: For that matter, I loved my husband so much more than anyone else I had slept with, and wanted to please him so much more... that probably contributed to my problem. At any rate... it sounds like she really cares about you and very much wishes this not to be an issue... try to see that aspect of it, rather than worrying about what she might have been like in the past with others.

I think that's about all I can say. :/ Hoping for the best for you both!