Answer: The numerous subscriptions to fashion and mainstream magazines she holds
b. See Explanation
Explanation: The external factor that may exacerbate Alexis' disordered eating is her constant exposure to models in fashion and mainstream publications. The modeling world is infamous for pressuring models to keep a low, unhealthy body weight. If Alexis perceives this as a standard weight for women, it could worsen her eating disorder.
The complete diagnostic criteria provided by the DSM–IV–TR for eating disorders comprise the criteria needed for diagnosing Binge Eating Disorder, Anorexia Nervosa, and Bulimia Nervosa.
Binge Eating Disorder: involves eating more than necessary to feel full within two hours, eating at a quicker pace than usual or doing so when not hungry. Any of these behaviors may occur at least twice a week over a period of six months.
Anorexia Nervosa: refers to an individual maintaining less than 85% of the ideal Body Mass Index, a standard measure for healthy body weight, and having missed more than two menstrual cycles.
Bulimia Nervosa: entails inducing purging, vomiting, or excessive exercise at least biweekly for a minimum of three months.
I did not discover Alexis' symptoms apart from those mentioned in the question.