I played the situation down a bit just to comment on how I have responded. My wife came from a poverty stricken area in the rural south and used to bring girls out here to Ca. at about high school age to see if she could give them a boost in life. Most of them had allready lived through pretty severe abuse and flirting with men to get what they wanted was about all they knew. So yes I have had more than my share of exposure to these issues and I am proud to say I behaved myself.
I was just joking. 
Why has no one given the obvious answer? You’ve already had too much to drink.
Just do the following.
- Sit up quickly
- Puke on her
- Go back to sleep
I’ve tried this more than once with women of legal age. I see no reason it can’t be applied to a teen.
Need answer fast?
Shag her and wait until morning to inform the parents they have a hot daughter. Between sips on coffee.
Do what you like–just make sure you don’t touch the leper daughter!
You win the thread by a mile.
Ding Ding Ding! Winner.
All you guys saying you tell the parents immediately are nuts. Don’t you remember what it was like to be 15? An unexpected accusation will likely lead to a panicky, ass-saving lie … and there’s really only one lie available to her … and who do you think her parents are going to believe? I generally roll my eyes at the men who are all atwitter about scheming bitches making up false rape accusations, but this scenario does sound pretty ass-puckering.
Rebuff her as kindly as possible and let it go. And document what happened: email/text your friends with the story as soon as possible.
I recall the scene from Animal House of the devil & the angel on the guy’s shoulder arguing what to do with the passed-out underage girl on the bed…