I have a 17 year old. We live in a large city in the US, so that will make a difference in my opinion.
Based on what you described, if my daughter had wanted to go in the dark in an unfamiliar wooded area, I would have said no. I would have also explained to her why and offered to discuss a compromise. Something like:
I know I am not your parent, but I am responsible for your safety while you are here. I am uncomfortable you being out alone at night in a less populated area you are unfamiliar with. How about you go out about in town where there are more people?
Unless, of course, it is just not safe. Then it is a "no, it is not safe" while thinking "you will thank me someday when you have kids.
I find the best way to keep a teenager not stroppy is to talk to them like the adults they almost are. Though, as we all know, sometimes teens just WANT to be stroppy and nothing you say/do will matter.