I would suggest looking into possible food allergies. Our Newfoundland gets a yeasty itch on his skin and we narrowed in down to poultry causing the flare ups. We now feed him a fish based food and it has helped a lot. Apoquel helps too if things get bad but is expensive, but worth it for his comfort. We also get our groomer to use Malaseb, which helps a lot too.

That doesn’t sound good! Have you taken your dog to a vet to see if there is an underlying issue ?

Our Cavoodle Mia has had food allergies that made her itch terribly. She would gnaw at herself repeatedly.
Once we took chicken totally out of her diet (which included reading all the labels on pet food), she totally stopped itching.
Could food allergies be causing problems for your girl?
Mia also has other allergies that are now causing her problems.
Dermcare have a range of Natural Shampoo products without chemicals, so we’re trying one of those.