How should I feel about a new girlfriend that explained she showed nude pictures of herself on the internet?

I just found out that someone who I saw casually 2 years ago and have been seeing seriously for about a month now was part of a web site where she showed completely nude pictures of herself. She claims it was something an ex of hers from the last 18 months got her to get into with him. It was not only a site where things are posted of that nature but people "chat" with eachother. She says that she never met anyone from the site during or after her previous relationship. She basically explained it was a "social" thing and that it was kind of a rush to have so many admirers. She is a beautiful, intelligent and wonderful person that I have known for many years now dating or otherwise. I honestly never saw this part of her though. We are at the point where much further closeness and an end to things could be painful. Should I end the relationship because of these differences? Should I let the past be the past? Does she expect the same "openeness" from me which she won't find? I give her the fact that she completely brought up the discussion about the site on her own and I would never have known had she not done so. She said she has always been faithful in relationships other than a fling in high school. I am not perfect either with my own difficulties and it didn't keep her from moving forward with me one bit when she found out about it. I have always given the relationship advice that if you couldn't be proud of having a child just like your potential mate then you shouldn't be dating them. I don't think I would be accepting of a daughter who put themselves out there like that at all. In other ways however this person has been there for me so much when she didn't have to be. I don't know what to do.