How long has she been doing it for?
You said that you didn't think anorexia or bulimia was an issue... Has she lost weight or failed to meet expected weight gains?

She might have a sore tooth. Or she might have a sore throat so it is painful to swallow. Or, since she mentioned a sore tummy, she might have a gastrointestinal disorder. Kids tend to say 'sore tummy' for any kind of pain, however (e.g., kids with earaches often complain of having a sore tummy) so it is hard to know.

I'd be interested to know what the doctor says...