Theres something your all missing and the reason why all your advice to the OP is worth squat...
You don't know the girls friends. you dont know the campsite but most important of all ..You have no idea about his daughter or what shes like... You dont know if shes little miss prim and proper who wouldn't say boo to a mouse or if she couldnt be trusted to answer the front door... none of you know anyhting about the family situation and yet your all offering these words of wisdom and advice as if you have read it from a book of parenting..
real life.. bit different..
16 yr old tattooed drug ridden alcaholic girls spend night with like minded friends on a gypo camp site... or 16 yr old girls spends night with brownies as part of duke of edinburgh award..... one extreme to the other but you dont know...
the only person who does know the answer is dad.... what the heck he is doing asking a bunch of photogrpahers on a forum is beyond me..
just my opinion... father of 7 all grown up.. 5 sons 2 daughters with one daughter more trouble than the other 6 put together