It really depends how mature your daughter is - and how sensible she is likely to be.
I would let her go, but sit her down for a casual talk about responsible behaviour - rergarding drink, drugs and sex.
Yes she will sigh and say "I know, you worry too much ..." but just tell her that you are saying all this so you can hear yourself saying it - as much for your benefit as hers!
Make sure she has all the safeguards she needs - proper clothing, mobile, contact info for emergencies, and wish her well.
It's hard letting go - but it has to be done - I have three daughters, youngest is eighteen, so i know how you feel.