Where is she chewing herself?
The thing that springs to mind for me is allergies.
If she has not been treated for fleas, I would go ahead and do that. I've had the best results with Advantage but others prefer Frontline. DO NOT use an over the counter flea treatment. They are not as effective and can be dangerous for cats.
Next, I'd look at a food allergy. Try to get her (slowly) onto a no grain, alternate meat wet food, like Natural Balance duck and pea. The must common triggers in food are: corn, fish, chicken, any glutens and soy. Food allergies can be a little tricky to pinpoint but, if your lucky, a simple change in diet can do the trick.
Since this all started in the summer, however, I would lean towards flea allergies.
If she's opened up a new wound, you really should bring her back to the vet (personally, I would try a different vet if they didn't discuss the above with you) It may need some antibiotics.
Hope that helps!