So she looked like an "angel", nerd, but good looking and you liked her breast size, or else you wouldn't have added that in.
But, then in bed with you she did "everything" which led you to ask her. You told her to be honest and when she did, (if it's true), you are now besides yourself.
If it's eating you up that much, let her go..
More importantly. Guess what? What happens in someone's past is their business not yours. It is of no importance what so ever, you don't own anyone and they are exactly that, a free spirit "before they meet you"...
Try in the future not asking... Maybe you can enjoy a fullfilling relationship that way..