What can cause hair loss with a 9 year old healthy well nourished active girl? what can be done?"

Hair loss in 9 y.o.: Conditions that most commonly cause hair loss in a 9 year old child include alopecia areata, telogen effluvium (due to interruption of hair growth cycle by illness, surgery, stress, meds, etc), tinea capitis (fungal infection of the scalp). There are also much more rare conditions as well. Whether something can be done depends on the cause. Please see your dermatologist for evaluation.