My mother was diagnosed with anorexia nervosa. Can you tell me about it?

Diet gone bad. Essentially it is another manifestation of a fat phobia. They tend to have overestimation of the possibility of weight gain with food intake - fearing that if they allow themselves to eat normally that they will inevitably and even suddenly become obese. The reflection offered from the mirror is distorted as imagined fatness/ugliness. Fasting is felt to squelch appetite - which is seen as an enemy.
Anorexia nervosa. Is an eating disorder which can be a serious problem. How old are you? Whatever your age, this is not your fault.