Teenagers on a Trip Alone

I know I shouldn't be worried, but my daughter and her friend have been looking at some different panama city beach resorts for this upcoming spring break. I realize my daughter is already in college, but she is still only 19. I just hope she is mature enough to be able to handle a trip just the two of them. I know I have to let her grow up, but it's always hard when your kids want to do things you've done and you know you weren't on your best behavior.