.
I agree very much with tony_danza - You need to trust her and she will respect you even more in her knowledge that you trusted her.
I trusted my daughter to travel with 3 of her friends to the South of France when she was 17. But I did drive down and visit them a week later - Just an excuse for me to go for a good drive. She's now 20 and went to New York and Warsaw last year, Paris a few weeks ago and Milan next month. I've just remembered that I allowed her to go camping locally when she was about 15.
Poll