Soulbliss
I don't have children myself but let me offer another perspective. You are older, the mom and have lot's of "arrows in the back" and are therefore rightfully jaded and fearful of the world out there. Your 15 year old daughter however, is just starting to spread her wings and is probably thrilled with wonder at each new experience that presents herself to her.
While you sit at home fretting about who might be there to comfort her (a perfectly NORMAL reaction), you look at "the glass half empty" in other words you are thinking that something's going to happen to her and you won't be there for her. You say that your daughter is 15 and very mature. Although the world is a scary place, I think you have to trust that you did a good job of raising her to be cautious when necessary but to embrace life.
It's not like you're sending her off to vacation herself in the Big Apple - most likely people will be there to monitor and herd the group together - sort of like organized tour guides for adults. And most adults will be quite accomodating in assisting anyone who asks for help.
Because of today's lifestyles, I hear of more people who are putting their kids as young as 10 years old on planes across the country. I think it's something the airlines are used to.
So... instead of fretting and maybe making her nervous about this, give her some good advice and then look forward to sharing this great experience with her. She is transitioning into the phase where she is starting to experience things herself anyway.
I sure do hope my words came out right because sometimes it seems like the words don't come out conveying what you intended

I'm just trying to remember how I felt taking those first steps to being a "grown up MOTHER".
In other things, I'm sorry I have been much more of a lurker than a participant this challenge. Some things have happened in my life - and a few have caused me to go on some medications right now. There are side effects and interactions to be dealt with, many of which playing havoc with the diet and exercise. I haven't been able to give it my all so I haven't been able to get much into the challenge this time. I'm sort of participating from the sidelines and have enjoyed trying to keep up with the threads. GO BLACK!