She likely suffers from low self-esteem and may begin to withdraw socially. Both diseases are psychological disorders that manifest themselves in eating habits. The common psychological component is the need to control. No one knows exactly what causes these eating disorders. Certainly our culture plays a big part, for there's little evidence of the disease in non-Western countries.
Stress also contributes to susceptibility.
My friend's daughter, Bea, lost a close friend in a severe accident right before she left for college. A series of other stressful events threw this bright Christian woman into the throes of anorexia. Fortunately, she has a close relationship with her parents and got the help she needed. Lynn had been struggling for months with an eating disorder. Her weight was falling rapidly and her mood swings were increasing.