I think more parents need to sit their daughters down and talk about self-image, what's a realistic weight, and what's not

And then, how many parents are the problem?

I think you're absolutely right about the approach. Her instructor should say something, and act on her own if need be. When I was coaching baseball, I always felt an obligation to look out for my players' health. It was easier, since Nate's dad is an ER doc, I wouldn't have had far to send them for evaluation or help. Hell, I still look out for them... once my people, always my people.