@cellmania- I can completely relate to what you’re saying. I was terrified the first time I allowed my daughter to go on a spring break trip. I was worried from the time she left until the time she walked back through the door three days later.
My suggestion would be to have a conversation with the mother that is chaperoning the trip. Let her know what your daughter is or isn’t allowed to do. Find out what she is planning to do to keep track of the girls. Basically, ask her anything that is on your mind.
Hopefully, this mother is a responsible adult and will make good decisions throughout the trip so that they can all have a good time.