cat going bald

My 12 year old cat has just started doing something strange right before Thanksgiving.  She is licking hair off her back.  Sometimes she rolls around like she is itchy and bites at these places.  Yet other times she can site for hours under my bed and just sit. This too is strange as she is not one that would hide. She is very overweight, declawed, and has always lived inside. I admit that she is totally spoiled. She is a completely gray tabby cat.  The bald spots do not appear to have sores nor are they oozing anything.  We do have a second cat so she is not lonely.  I called my vet hoping for answers as I am a college student and I do NOT have the money to take her in. The vet suggested a flea treatment and I did give her this for awhile although I have not seen any signs of fleas either on her or my other cat.  The vet also suggested mites and after brushing her, I have not found any signs of mites.  Her food and liter has not changed so I cannot fathom that she could have an allergy.  The only thing that is different in the environment are the houseplants that came in from outside.  I don't know the names of the houseplants so I don't know if any that we have are bad for my cat.  I can't get rid of the plants as they don't belong to me.  Help!!!

[Kaydey]

mites will often show up loose or dry skin.  there is also the possibility of allergies (which can show up at any age of the cat and it doesn't have to be food or litter), and stress will also cause a cat to lick until the hair is gone.

There are so many things that could cause a cat to lick off their own hair.  

I would suggest you figure out what plants you brought in, look to see if she is nibbling on them.  So many plants are toxic to animals.

Also, it would be helpful to know the age of your cat, if she is up to date on vaccs. etc