Questions about anorexia?

I know somebody whom is 5,6, 16 years old, and weighs 90 pounds. She previously weighed 86 pounds last year. If you saw her, you would probably think rail or skeleton. I am confused about her condition because there is a rumor that she has a thyroid disorder. She does not have a swollen thyroid gland, or displays nervousness. Her neck is rather a sickening tube with arteries dangling. She also never eats anything. All of her food is cut-calories, low-fat, diet, vegetarian, little salads (etc.) and she is a health freak. In gym cl while everybody is bench pressing, doing push-ups, using dumbbells, she is using the cardio bike secretly on the weight burner mode and rigorously working out for the whole cl. Another time, she tore a ligament in her ankle and was left on crutches for over a year. She also displays a body a too small for her head (decreased bone density) and is a raging perfectionist. Is the rumor about hyperthyroidism false, or is she really anorexic?