what if your girlfriend has been......?

I think it depends on how strong you feel for her. If you truly love her then you should be able to look past that and take solace in knowing that she is with you now. It would have been nice to know it up front, my fiancee and I knew about each other past relationships from the beginning. That's life, you just have to be able to look over it because let's face it, the chances of you finding someone who is a virgin is very slim. It happens but not often. I say you proceed with the relationship as long as she has been faithful with you since you've been together.