This is actually a favorite technique of women behaving badly. They do something that’s obviously wrong or that looks terrible and when you call them on it, they play babe in the woods. Via Reddit:
My Gf (21F) cheated on me (21M) and claims you not remember.
My girlfriend and I have been dating for almost a year and she’s everything I’ve ever wanted. I love her a lot and have always had complete trust in her. We are doing long-distance (7 hour drive) but are both very in love with each other, or at least I thought. She has a group of about three guy friends that she studies with and nothing more. They invited her out to a party the night after finals and she went with her roommate and roommates boyfriend. That night she got very drunk and claims to have blacked out. The group of guys all have girlfriends except for one, which I have always been suspicious of. That night, they get very drunk at the party and she and two of the guys go to the bar. The one guy who doesn’t have a girlfriend claims that my Gf and the other friend made out all night at the bar and she was “straddling him like a monkey.” She denied any knowledge of this event until it had been completely proven to me and then she said she doesn’t remember it but she was told what happened the next morning but didn’t want to hurt me. I’ve been kept in the dark about this for over a month. I don’t know what to do. I still love her but I feel hopeless. Any and all advice is encouraged.
TLDR: Girlfriend made out with her friend at a bar. Claims it was blackout but knew event happened and refused to tell me for over a month.