Party sex!

I fucked my best friend's crush at a party last night! I haven't told her and I really don't want to because I was super drunk and barely remember it. All I remember is him pulling my leg over him so he could "get comfortable" then the next thing I remember he is on top of me, I remember being into it but I feel awful and he is leaving for military training soon. She is already pissed at me because he kissed me. I need advice. Should I tell her?