Okay, first of all you must realize she will be damaged for years. I've been through a lot of shit as well, and it took years to get to where I am now. Maybe you should just go on a few dates with the girl you like and just see how it feels. If you find out you really like her it could be time for you to move on to something better and part ways with your girlfriend. If you are happy with your girlfriend you should stay with her though, but don't stay with her to help her, or because you feel sorry for her. Only she can really help herself.