I was chatting with my wife about this last night.... few points we discussed and agreed upon.
1. Age doesn't matter, I would have let her do it.
2. For me the ability and skills to run the boat is not the issue, she's probably better than most.
3. Since she is under age and as a parent I am responsible for the safety and well being of my children. To take on such a task the parent should make sure she has the proper support network to keep her safe should something happen... You know, like how an abulance and EMT's are always onsite at a kids football, basketball or other sports...... Some type of rescue boat or support system should have been "nearby" to rescue her if there was a problem... IN this case, she may not have even needed to be rescued since she was found alive and well but no one would have lost contact with her. I'd never send my kid out to do something like that by themselves.
So in summary, my wife and I wouldn't stop her from doing something but what we would mandate, since we're still responsible for her, is that it done properly and as safely as possible with the proper support network.... If that support network cost $500K and I didn't have the cash to support it well, then she can't go.....