Hm. Is she chewing very hard, like breaking the skin? My kitty would often lick her paw, or lick my arm, or whatever was closest to the mouth, pretty furiously for a few seconds when I brushed certain parts of her, primarily near the base of her tail or along her hind legs. When I stopped brushing, she stopped licking. And as far as I can figure, it was a positive response. I think it almost tickled, and she didn't know how to react to that.
There is something called feline hyperesthesia syndrome. Some cats are very sensitive to being touched. It can be mild or very severe, but usually, you'll see kitties with rippled fur. I don't know quite how to explain, but if you look this up, you'll find videos.
The only other thing I can think of is that she's itchy. Do you ever see her licking, chewing, or biting her fur?