Are you taking treatment from a dermatologist? If no, see a dermatologist please. She has premature graying of hair. A lot of factors can trigger that. If yes, then please understand that graying of hair is very difficult to treat. A lot of counseling is needed because at times the hair do not return to the normal black colour. I don't mean to be negative, I'm just being honest. You could also think of getting help from a psychological counsellor. Counseling helps relax the patient. Also, a pediatricians advise on whether she is in the right  'weight for age'  category might help. All in all, don't lose patience.