Hello, no worries about jumping in the thread. I'm genuinely sorry to hear of your situation. My own opinion is that you need to bring this knowledge to her attention, regardless of what you choose to do with the relationship. I mean, if you want to continue with her, it must be dealt with. If you choose to move on, it will serve as the basis for the move. Your choice will also have an influence, I would think, on how you approach her with it.
I would also suggest, if you don't have absolute validation of your hunch, to get it. This can be done in many ways, including a private investigator. It may turn out that your hunch is incorrect. Hiring a PI can give you peace of mind or validation.
The reason I say have your proof before you confront her is obvious. If you don't have it, all she has to do is deny it, and you're back at square one. Moreover, she will be tipped off to what you are thinking and will begin to better cover her tracks.
If you're in the southern Calif. area and decide to go this route, let me know, I can hook you up.
I'm hoping that your hunch is incorrect, and there is a reasonable explanation. However, regardless, it must be addressed. Good luck.