My suspicion is that there she neither experienced ordinary discomfort nor does she have a faulty metabolism. Rather, it's possible that her weight loss strategy was far too extreme.

Yes now that I think about it that's the most likely explanation. I've been informally researching diet and weight loss for nearly two years now. One thing I've informally observed is that self-deception is a big problem in dieting. Thus when failed dieters report on their failure, they have a tendency to underestimate their caloric intake; they also have a tendency to assert that there is something wrong with their metabolism.