Have you looked at the skin in the back? Some painful skin disorders included Feline Acne, Impetigo (pus filled blisters) and Abscess (painful, hot, inflamed skin or pockets of pus beneath the skin). Also, hair loss can be caused by diseases such as Ulcers, ringworm, mange etc. Perhaps, being the fact that she was stray, she has ringworms, but only a vet should give a full diagnosis. Tapeworms and other fungal problems can be treated utilizing a 2% solution of OX-E-DROPS or Tincture of Black Leaf. The best thing to do is to get her examined by the vet.
Also, for declawed cats it is recommended to have them inside at all times. It's true, some can still climb and haunt but it's just not safe. I can tell you a story. I once had a black cat who loved to be outside, so I let her. She was not declawed because she was outside almost all the time. One day two dogs came after her. In her attempt to run away for dear life she fell in a huge swamp. She started swiming in order to not drawn. When she got tired of swiming she got out, but the dogs were still there, barking and waiting to attack, which they did, after she got out. She had claws, very sharp claws, and still could not do anything to save her from major injuries in her spinal. She returned home limping, disaster. She could never walk again. She was too damaged. Can you imagine if this were to happen to your already found declawed cat? Just an advice based on my own experiences. :)
Please let us know what the vet said. Good Luck.
Has she been de-wormed at all? Are you bathing her with a different shampoo? It could be an environmental or chemical skin irritation. My guess is to take her to a vet, but maybe in the meantime try de-worming her and try some advantage or revolution (a de-flea and parasite drop of liquid at the back of the neck), as sometimes revolution covers a few more parasites than the worming paste alone.
Best of luck.
I agree with AussieKitten81. Shampoo is also very important. Don't bathe her with shampoo that's not for cats. If you haven't given her a bath you can start from there; and take her to the vet. Also, have her checked for ear mites.