fur loss in cat

Question
my cat (Libby) seems to be loosing her fur at the bottom of her back down to the base of her tail. I don't know if she is chewing herself or if its just falling out, i don't see her doing anything to herself but there are some very small cuts on her skin. Some things that could help you is that i have another cat (Oreo) who is fine and a dog (Magoo)who also seems to be fine there is no hair loss on either of the two. i do have a 3 1/2 year old who likes to be pretty rough with Libby and i think but am not possitive that this sarted happening when my daughter started getting rougher with "her" cat. Anything you could tell me would be greatly appreciated. Thank you for your time  

Answer
As a precaution, I would use Advantage to treat for any possible fleas as this is the area that fleas tend to bite.  Otherwise, a trip to the vet is warranted...she may need antibiotics since her skin is cut up and possible a steroid injection to settle the inflammation in her skin.  Cats can lick themselves excessively from anxiety or stress but usually they will do that on their belly.