well i was only 16 four years ago so being that age is very fresh in my mind. Does ur DD have a mobile in which u can contact her during the night??? My mum used to do this. She would ring me anout 10pm to see how i was going and to see if i wanted to come home.. then she would ring again at midnight. I didnt mind this even tho in the back of my mind she was just checking up on me but i thought it was cool that she cared so much but she was still letting me do what i wanted to do.
All i can say hun is.. if u feel really uncomfortable about letting her stay the night then dont!! mother intuition is what u should trust. This wont mean ur not trusting her u just dont trust the situation.. eg alcohol etc.
Honestly if it was my daughter (which i know its not it just my opinion) i would go and pick her up about 12am-1am ish... only for my own peice of mind. Trust me 16 year olds can get abit crazy!!

Hope this helps. xoxo