I’m thinking the school and the teacher are fully aware of the student’s challenges, right? The student likely has an IEP and regular meetings with the parents and school to make sure special needs are met. I would hope that the school is preparing with the parents for the best way to help the student on the trip.
My high school nephew with ASD is on a team that travels regularly for competition on the weekends. The school requires a parent to go with him because they don’t think he is ready to manage without that. He needs help when plans change, and when his expectations don’t match reality. He also does not intuitively know that some things are against the rules without being directly told, which can get him into trouble. However, he’s in 9th grade. I could see him maturing and being able to handle the trip without a parent in the future.
I hope your D has a wonderful time! I went on a school trip like this in high school and it was a positive and mind-opening experience. I do hope she, or some student on the trip, is mature enough to be a friend to the student with ASD. My nephew is often lonely, which breaks our hearts, although we understand that many people can’t get past his quirky behavior.