In Maryland the age rule is irrelevant when you are a "person of authority".
Yes, she/he can be 16/17 and it's OK. But when you are a teacher, doctor, police within that venue for the profession it's illegal. I think that might have been the issue here, not sure.
Yes and as much as I don't like conditions, despite their being good cause in this case, that wasn't the question presented.
Besides, she is a volunteer coach for the cheerleading squad. I'm not sure I'd consider that a position of power over a 17 year old boy even if he was on the squad.