<p>Come to think of it, I was 21 before I paid for/booked my first hotel room. Theoretically, your daughter and her friend should have no trouble booking the room as long as there’s a credit/debit card to go with the reservation. I don’t think I would have liked to travel alone when I was a senior in high school, I was definitely not ready, but having done so, it’s not bad, and would be fine with a friend.</p>