Replying to HUGE DILEMMA need help

so like 3 days ago i was partyin at my girlfriends place with her(rachel) and her roommate ali. so rachel(the gf) get compltly shit faced yells at me for some shit i dont even remember, i was pretty drunk to, and storms off to bed to go to sleep. well now its jus me and ali drinkin and like we have partyed together alone and been fine yea there was flirtin but nothin could happen cus she was my girlfriends room mate. i dont know what the fuck came over me that night but long story short by about 4 in the morinin i was in ali's bed and we were goin at it. the next mornin was so awkward but idk ali is so much better at screwwin then my girl is, lol. so anyways now ali tells me she feels like a slut and never wants to talk to me until im single.

i guess i dont want to lose ali's friendship cause she is an awsome chick but i aint ready to ditch my girl. WTF. `