<human>: This past weekend I was out drinking with my gf and a group of friends. We all got completely hammered and I ended up going back to my place with my girlfriend and one of our female friends that had nowhere to go. We all crashed in my bed and I started getting sexual with my girlfriend when she suggested a threesome. I was surprised but went along with it and ended up fingering and kissing the other girl along with my gf, from there my memory is hazy but I don't think any sex happened, we all ended up passing out. So the next morning I wake up to my girlfriend freaking out about this other naked girl in the bed and she does not remember anything. I had to explain everything to her and she was very upset saying that is not something that she would ever want. Now she is not sure what to do. I feel so guilty like I cheated on her and she doesn't know if she can get over this. We both love eachother but we want a healthy relationship and if she cannot get this out of her mind I know it wont be.

Can you succinctly summarize the text in 1-3 sentences?
<bot>: Had a blackout threesome with gf. She is upset and doesn't know if she can ever forget about it.