I did let my daughters stay over their friend's house after prom, but I always told them that they could call me anytime for a ride home. Sometimes they wished they had just come home because the party was going on too long and it was just not all of the great fun they had expected. I had to go get her and her date once and I'm glad that she called me. My oldest is 30 and my youngest is 25 so that was quite some time ago. They still know that I will come and pick them up if they get stuck someplace. It depends on the circumstances everytime, but if you talk about what your expectations are, she will have already made her decision about what she wants to do before a situation happerns.