SHOULD I DUMP HER??!!??!!?

My gf and I have been planning on marriage for a long time. She and I have now committed but I want to back out. The reason is I don't know how I can cope with the fact that she sucked some guys dick before. This bothers me because she lied to me. She told me that she was a virgin and that she was my one and only and that she was saving herself for me. When I engaged in foreplay with her, I felt it was loose. And then I brought up the issue. That is when she told me that she was abused by three guys and that one of them made her give him a b j, the other made fingered her, and the other made her play with his penis. I don't think it was abuse because she never told the cops anything. Then she told me that she was still a virgin that no guys penis ever went into her, but told me that she had tried to fit fingers in there and play with her self and perhaps thats why she has a mangled up vagina. She made the comment that when I fingered her and put in two fingers she has never felt so much pain, but wow I don't know what to believe. She also said that thats the only thing she managed to save, and that she would go to the doctor to get it checked out and prove to me she is virgin. So now I don't know what to do anymore.