Ellen is underweight but not less than 85 percent of normal body weight. she often restricts her eating because she is intensely fearful of becoming fat. she purges at least twice a week, even though she does not eat large amounts of food at any sitting. according to the dsm-5 she should be diagnosed with

I think she should be diagnosed with purging disorder.
Purging disorder is an eating disorder characterized by recurrent purging to control weight or shape in the absence of binge eating episodes. The symptoms include; disappearance of large amounts of food, eating in secrecy, lack of control when eating, switching between periods of overeacting and fasting, and frequent use of the bathroom after meals among others.