I wouldn't like that either. Are they all from the same school? Do you know any of the parents? If so, they might know some of the others.
Offer to give her/them lifts and make your house a welcoming place for them to hang out. Try to explain the embarrassing consequences of having too much to drink IMO that's more likely than a lecture on safety to put her off having too much alcohol.
Make sure she knows that you will go and get her out of any situation at a moment's notice if need be, agree on a code word she can use if she doesn't want other people knowing she's contacting you then wave her off with a cheerful, 'Have fun'.
I used to go off with a group of friends to the local pubs (small town/rural area) when I was a bit older than your DD (the pubs used to let us in without ID if we behaved - this was back in the dark ages) and my mum regularly used to tell me off for not coming in when she'd said I should be back home. I don't know if this applies to your DD, but I didn't give two hoots for the fact she worried - as far as I was concerned I was sensible, my friends were sensible; if my mum was stupid enough to worry needlessly it was her problem, not mine. 
Obviously I was too immature to respect my DM's feelings, but as far as I was concerned there was no problem - and actually there wasn't. Your DD won't be worried about her safety either.
Try to listen to her without commenting too much/being shocked/horrified/judgmental so that she feels able to tell you things.