Clearly, someone needed to take the school district to task over this. Administrators and teachers routinely overlook bullying- I know this very well. Some officials deliberately turn a blind eye, while others simply have no clue. Bullying is hurtful and harmful, regardless of whether it results in an eating disorder or not.
However... the bullying didn't cause this poor girl's anorexia. It might have triggered it, yes, in the sense that the bullying caused her to throw her lunch away, which led to the energy imbalance, which led to anorexia. But it didn't cause her anorexia. Science shows us that genetics form the biggest risk factor for eating disorders, although many environmental factors can play a role in triggering the disorder. This type of bullying is sadly common, and if every case resulted in anorexia, we would have many more cases of eating disorders than we presently do.
Will this girl benefit from some good therapy to help her deal with the bullying? Absolutely! It caused real distress, even outside the eating disorder. What we don't know is whether she might have developed AN if she hadn't been bullied, or if administration officials had stepped in. Maybe she would have, maybe she wouldn't. We just don't know.
Schools should refuse to tolerate bullying because it's harmful and wrong, not just because someone developed an eating disorder. I'm not naive enough to think that bullying will ever stop, but we can stop accepting it as a normal phase of growing up. And that's a good thing even if it has no effect on the number of cases of eating disorders.