I have a staffie who also scratches a LOT and loses a lot of fur. The only way I've managed to control this, even with trying all the fancy pet products, is using anti dandruff shampoo for humans, but ONLY certain brands that aren't harsh, like Head & Shoulders. I dont know what country your in and if you have that brand, but if so, give it ago
The beauty part of these dogs are their skin. They can have the same skin products as us and it usually works. Try and find an anti itch topical cream for humans and apply it to her and it just might do the trick!
I had an american red nose pit bull and if he had a cut, I would put polysporin, if his skin was dry I would put keri lotion and it all really worked without fail. So I would try that. Hope it helps!
I don't know what is the cause of this, considering you have tried more or less anything, so far to treat it. However, I know herbal remedies do often work (not always, but it might be worth trying if you are interested.) I'd try bathing the affected areas with a tea made of Burdock Root / Marigold Flowers / Yellow Dock. A teaspoon of each/1 cup boiling water/steep15 mins/strain/cool. Use on a pad of cotton wool 3-4 times a day. Try it for a few days, and if there's no change, I'd take her back to see the vet.