I really need help with this one..my girl friend was d and im having a really hard time with it..?

about 2 months ago my girl friend was at a friends house she was drinkin and 2 guys came over well the one did end up taking advantage of her. At first i didn t know what to believe but after some of the behaviors she was showing i do believe she was d..right after this happened she tried over dosing on pills and she was ashamed to change in front of people. Before any of this happened she was very innocent i was her only ual partner and her and i planned on getting married she was very stable with everything.. But after it happened she tried over dosing she cut her wrist once and she cried almost all of the time. Through out all of this i have stuck by her side all the way but its killing me inside thinking about what happened to her. i love her so much and i really do wanna spend the rest of my life with her and im tryin to block out all the drama coming from everyone else. i just really want this to be over and move on but i dont know how to or what im suppose to do..