There could potentially be a broader story here -- maybe even a good one. But, serious care needs to be taken not to make assumptions or make this episode out to be more than it may actually be, too.
There is a big difference between a girl "trying to lose weight" and not eating enough, possibly out of inexperience, lack of knowledge, and a desire to watch her weight, and then, perhaps, suffering the consequences one time when she overexerts and overtaxes her body -- and someone who is actually suffering from anorexia nervosa, or exercise addiction.
People who are dieting -- including many adults -- often have done the former, not taking in enough nutrients, calories or liquid for what they're doing, because they're trying to lose a few pounds and just aren't being conscious or careful enough about what they are, or are not ingesting. It's just a mistake, a risk, that people make/take, out of ignorance or in hopes that the benefits will outweigh that risk. Sometimes, they don't even know or think there will be problems.
It is a physical, physiological issue with the body that will arise with anyone, beyond a certain point, and in certain circumstances.
People with anorexia, by contrast, are conscious of every single morsel they do or do not put into their mouths. Contrary to many just trying to lose weight, they know just exactly what they are doing, and their self-image is distorted to an extreme and potentially dangerous degree.
In short, it is primarily a psychological problem, relatively rare, and will not, and does not, happen with everyone who is trying to lose weight.
Big difference.
I would not assume this girl has any kind of eating disorder (unless the coach told rpm something to that effect on an off-the-record basis, which is almost what his "out" and suggestion of "protection" sounds like).
Not without lots more serious, in-depth reporting.