You suspect that your new college roommate may have an eating disorder because, although she seems to have a normal body size, you have heard her frequently vomiting after a meal, and her tooth enamel is becoming corroded. she also will frequently eat 3 boxes of crackers at one time to relieve stress and will then feel guilty afterwards. these are most likely symptoms of:

The answer is Bulimia Nervosa

Explanation:

Bulimia Nervosa is one of the most common eating disorders; this is related to anxiety and body dysmorphia that makes an individual eat compulsively (binge eating) and then look for ways to compensate this, such as taking laxatives or self-induced vomiting. Due to this unhealthy cycle, most patients experience mood swings, dental problems such as damage to tooth enamel, and digestive problems, although they might have a normal body size and weight because in some cases it occurs only through episodes few times a week.

In the case presented, your college's symptoms are symptoms of Bulimia Nervosa because she shows anxiety that makes her eat compulsively; also, after she eats she induces vomiting as a way to purge herself. Besides this, she already shows dental issues but still has a normal body size which are all indicators for Bulimia Nervosa.