<human>: Condense the text into a few key points

So I am seeing a girl (dating). She leaves in February. She is best friends with my best friends girlfriend. She had one stipulation - Don't sleep with anyone else. On top of that I know she is beginning to like me. When we first started dating she told me not to get to attached as she was leaving. So I have been cutting away all feelings after each time I see her but recently things have started to linger really heavily. Well. I became really intoxicated and slept with a coworker at a staff party (this is very out of character for me). The next day when I dropped her off she treated me like a hookup and hasn't contacted me since (4 days ago) To further complicate things the girl I slept with is friends with my best friends girl friend as well or at least has a good acquaintance relationship as they used to work together. Now I know this situation is a ticking time bomb. I don't want to unnecessarily hurt the girl I am seeings feelings and destroy my relationship with my best friends girl friend ( we get along very well ) To be honest I don't care how much emotional harm happens to me or actual harm. I just don't want to hurt the girl that had nothing to do with anything.
<bot>: dating a girl where feelings are manifesting. Got wasted slept with a girl in the same social circle at a staff party. Need to not hurt first girl.