<human>: Could you distill the essence of the text into 1-3 sentences?

So basically she calls me and says we need to talk, and I'm honestly not really expecting anything. She then commences to tell me that she's really really sorry and that she was going to tell me in person but I had insisted. She said she didn't remember anything and that her friend had told her what happened and it jogged her memory, but I doubt it since she told me with grueling detail.

She was at her friends farm with two other girls and 3 other guys. They  were drinking alcohol and "chilling" in the barn. She left something in the house and was accompanied by one of the guys. The guy attempted to kiss her on the way walking back to the house but she had turned it down and according to her, slapped him across the face since she was sober. This was the "first attempt" from the guy to start anything. The night ensues and everyone gets wasted according to my girlfriend. Then the same guy makes a "second attempt" and kisses her. From there they commence to do "everything but have sex." And then she tells me that it was "horrible" in a failed attempt to make me feel better. 

In one of my past relationships I had cheated on my ex with another girl while drunk and I had gotten in an argument with my current girlfriend about it. She was threatening to break up with me because she said "once a cheater is always a cheater." But now she contradicted everything she stood on in that argument.

I honestly don't know what to do, my flight leaves in 2 hours and we had planned to hang out when I got back, but now I'm not sure if thats what i want to do.
<bot>: Girlfriend calls me when I've been out of town for a week and says that she cheated one me when she was drunk. I don't know what to do.