I started to have sex with my cousin’s friend in a front of her

2 years ago i was partying and my cousin and her bestfriend were there. We all drank way too much that night. we were all 3 of us in the room, and then her bestfriend said “i want to kiss someone” impulsively i kissed her, because of the amount of alcohol i drank. And then suddenly everything went black for a moment and when i opened my eyes i was lying down on the ground all weak and i saw her on top of me, we kissed really hardly and she started to touch me. My cousin was there and was seeing all this really confused and disgusted, she asked us to stop but she was drunk asf, and too weak to separate us, and i was too weak to stop anything, we just kept going a bit and i dont know how it ended up. Its really embarrassing and we arent even lesbian. Whenever i see my cousin i cant stop thinking about it.