I made a mistake that I don't know how to fix?

[Amy]

I used to hook up with this boy all the time, but then one of my friends started dating him. I didn't care at all because I didn't like the kid. him and my friend dated for almost a year and they broke up. when they were broken up, I was at a party with him and he got me in a room with him and we started hooking up but I made him stop because I didn't want to hurt my friend. I didn't tell my friend what happened and a couple days later, she got back together with the boy. about 4 months went by and we were still friends but she found out about what happened at the party from someone else and now she hates me. I tried to explain myself and I aplogiZed several times. it makes me so upset that I hurt my friend and she won't even speak to me