How do l stop my cat from scratching a wound on her face without using that cone?

You didn't mention if your cat has been to the vets yet. It's obvious there is some form of dermatitis going on or something else. If you have been to the vet then the collar must be left on to give the medication a chance to work. If you haven't been to the vet for a diagnosis on your cat please do so as soon as possible.