“What makes someone addicted to food?”

See a therapist immediately. Also, find a good bariatrician in your area through www.obesitymedicine.org as she might need medications to treat the disorder.

Anorexia-bulimia can occur in teenagers for a number of reasons, but basically, it's a body image issue or coping mechanism in some who have been bullied or abused in some form. This should be taken seriously and should be in individual or group therapy. She may also need medication to address underlying anxiety.

"Binge eating disorder" is a recognized problem. It's not an addiction but is more or less in the same family of problems. Your daughter needs treatment through an eating disorder program. On rare occasion, you can find a psychotherapist with expertise in this area, but more commonly therapists say they treatment eating disorders but have none of the required extra training. A formal program is a better bet. Most likely, she would do fine in an outpatient program, but there's no way to tell what level of care she requires without a formal, person-to-person evaluation.

Check this link out...
https://www.virtua.org/articles/what-causes-food-addiction-and-what-are-the-signs
or
https://www.eatingdisorderhope.com/information/food-addiction

Usually, binge eating is tied to some sort of trauma, anxiety or depression. Food is usually used as what people call comfort food....they use food as an emotional escape. Your best decision would be to seek professional help with a psychologist.