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I am Dr. Snow, and I can try and help you with Charlie. Scratching and sores can be several different things, and sometimes it bothers them so much that their behavior changes. Do you have any other pets that could have brought fleas in? She may need a flea treatment regardless, and if she is that itchy, your veterinarian would be able to prescribe some medication to help. Itchiness and sores can also be due to allergies, such as food sensitivities or environmental allergens.
Your local pet store should have some topical allergy relief treatments available that may help. Sometimes applying some coconut oil to the skin (which is safe to be ingested) can help the sores.
Please post back with further questions.