<human>: Can you provide a brief rundown of the text in within 3 sentences?

I just turned 18 and I had my birthday party out in the middle of no where just gettin' tore back with all my friends. This girl shows up, and she's not bad looking, definitely not gorgeous though. I didn't know her, and in my drunken stupor I said something along the lines of, "Heeeellllooooo my name is ***** whoooo aree you???? It's my biiirrrthhhhhdayyy... FUCK YEAH!" So I was hanging out with her for awhile around the camp fire, got to know her and what not, and she ends up telling me that she is only 15. At this point I'm like OFF FUCKING LIMITS GTFO BITCH. I guess I kind of hurt her feelings, and she went to be comforted by someone that she knew who happened to be a really close friend of mine. My friend, whos name I won't disclose, is 20 years old. The 15 year old girl and my 20 year old friend ended up doin' the nasty, and not only do I feel awkward, I almost feel kind of responsible... I feel like I should have protected her from a situation like that even though I didn't know her. She was only 15 and was incredibly too drunk to make good decisions. What should I do? Should I contact this girl? Should I approach my friend about the matter?
<bot>: At my 18th birthday party some 15 year old chick got boned by a 20 year old, and I have a slight feeling that it's somewhat my fault.