She also scratches near the front of her ears. I thought she had ear mites. There are a lot of causes of itchy skin, especially around the ears and head, in cats. It is unlikely that this is due to ear mites since your cat has been examined, but that is a possible cause. Cats get several types of mite infestations, including demodecosis, cheyletielliosis and notoedric mange.
Allergies can cause itching and some cats with allergies have increased dander.
Viral infections, such as herpes virus and feline leukemia virus sometimes cause scabby itchy sores on the head or other areas of the body. Phemphigus foliaceus, an immune mediated disease, can cause itchiness around the face and head. There are probably other conditions that I can't think of right now. It is probably going to be necessary to do more diagnostic testing and possibly to try treating for some other conditions, in order to finally find a diagnosis and appropriate treatment. Fungal cultures for ringworm, using a toothbrush culture technique, can be helpful as an early test since it is easy to do and not very expensive.