what is the actual source for nyasha's eating disorder?

Nyasha is a perfectionist. Everything has to be perfect. Both her studies and her figure are a concern, but unlike her studies or even the cultural issues she deals with, her body is the one thing she has control over.

Anorexia is virtually unheard of in women from Rhodesia, but during her time in Europe, Nyasha was heavily influenced by Western culture. Her time in England left her exposed to European values and customs. Things such as clothing, body image, and wealth (unheard of at home) were at the forefront of importance and left their mark.