I think it sounds like a wonderful opportunity. Even if she doesn't end up dancing, she will learn a lot from it.

Here are my questions:

1. How badly does your daughter want to go?
2. How are your daughter's life skills? i.e. taking care of herself, keeping house, making food etc.
3. How are your daughter's executive function skills? i.e. can she be on time, keep track of her things?
4. Any street smarts? Is she aware of her surroundings? Good intuition?
5. You say there will be constant supervision. How do you know? I would ask specific questions about every part of the day. What happens if she gets separated from the group? How many chaperones?

Here's one story about my daughter - she was only 14 though at the time. My daughter made the varsity high school dance team the summer before she started her freshman year of HS. In August, there was a mandatory (one week I think) dance team camp in Charlottesville. I was assured that the girls, ranging in age from 14-18 would be well supervised. They stayed on campus in dorms. Ate in the dining hall. There were about 14-15 girls on the trip. I was told they would be in clinic/camp all day, walk as a team to the dining hall, and there would be bed checks each night. That wasn't the problem. The problem was when my 14 yr old daughter who had ADHD and executive function issues, walked with the team to the dining hall realized she had forgotten her dining pass. The adult coaches weren't there because they had decided to have dinner with the other HS team coaches and left the 18 yr old students in charge of the rest of the team. They didn't want to make everyone walk back to the dorm for my daughter's pass, so they told her to sit by herself on the bench outside the dining hall while they went in for dinner. They would bring out dinner to her when they were finished.

So there's my 14 year old daughter, who hadn't even started high school, 150 miles away at UVA, sitting on a bench by herself while there was a MURDERER (victim Morgan Harrington) on the loose in the town. My daughter didn't even tell me about it until a year later because she knew I'd freak out.

Anyway, I thought I had asked all the questions and they were answered properly...until the coaches changed the agreed upon plan. Your daughter is older and more mature, and she may not have any of the issues that my daughter did (even in the small town), but I'd make sure there is a contingency plan and the chaperones know they are not to deviate from the agreed upon plan.