Your friend meets 3 of the criteria for anorexia. Her appropriate weight is 101 to 136 pounds. Anyone who has lost 22% of her/his healthy weight has one symptom of anorexia.
She also has an inaccurate perception of her body. A person weighing 86 pounds probably does not have much fat on her stomach at all. The “fat pinch” they grab is skin with little underlying tissue, not fat. People with anorexia strive for body perfection and a fanatical control of their weight.
Candy is a common binge food and I would imagine your friend might also have some bulimic behavior. Though, I am surprised that she would eat candy in front of you. Typically, persons with bulimia don’t eat binge on food in front of other people. People with anorexia don’t eat much at all in front of others.
I would suggest you encourage her to seek professional help. Be supportive and offer to accompany her to a mental health appointment. Tell her that she looks unhealthy, not thin. If she denies that she needs help, continue to tell her that she doesn’t look healthy and encourage her to seek treatment.