Do I get back with my girlfriend fully?

Hey, me and my girlfriend have been together for a year and a half, things were going so great, but we started arguing a lot while drunk and it was mostly my fault because I tend to dwell on things to much and make them worse than they are! Well we were out last sunday works doo and a college of mine started insinuating to me that I didnt want to be with her no more, and I was extremy pist and we had argued very badly the day before so stupidly I started to agree with this person, which I know now I did not went, so this person aproached my girlfriend later that night and told her infront of everyone I dont love her no more and that I dont want to be with er about 5 times, she then broke down crying apparently, she claims she came to me and I was hurling abuse to her, I remember coming to my sense and trying to ask her what was wrong casue I was unaware of all of this, and she pushed me away and refused to talk with me, I then went out for a cigerate and couldnt get back in the club casue the bouncer said I was too pist, so she went to another club with her mates and ended up catching a mini bus back with her mates and a load of guys, she eneded up going off with a bloke on the bus and going back to his house and having sex with him, I cant really remember what I said that nite to our work collouges but a lot of people approached her with the news and I called her a slag to her friends, I dont know why I did this but I was so drunk and I feel that people pushed our end that nite, like I was brainwashed into saying iddint want to be with her due to our troubled last few days of arguning which upset me and they were pety and not needed

She says she doesnt know why it happened , she says that she felt so alone and upset that this guy played her and made her feel wanted and that she is biterlly disguseted with herself and hates herself for what she has done, she said she told him sex was not going to happen, he said he would sleep on couch and she had bed, and he came in 15 mins later and kept trying it on with her. I only found out when her story as to where she stayed was full of holes and I could tell sumthing was up, she then started begging me for her to take me back and telling me how much she loves me and thins will never happen again and that it wasnt cheating as such as we were finished in her eyes, but I cant cope with how eaily she slept with someone or is it befcasue I had upset her so much that this guy just played her casue he knew she had just finished with her me, her boyfriend. I can see that she truly regrets what happend but I’ve started to be in contact with her after a few days but im finding it real hard to forgive and forget this , do you think I should forgive her and try and move on and salvage the relationship I have with a girl that was the one for me before this? We have spent every day together since the start, or do I just cut my losses now in fear of this happening again, any adive would be great, I just want to beleive her so much and part of me does beleive she is telling the truth, but part of me thinks she went with someone to easy, I have never cheated on her, we are each others first loves im 22 she 19,