I learned (the hard way) that one of the signs of a dog in pain is self-mutilation (chewing or licking themselves excessively). Can you get her to a vet to determine if it is a foot problem or a sign of something else?
Have you examined her feet to see if she's picked up a splinter or has a small wound? If you live in a hot climate, could she have burned her pads? If in a cold climate, snow-melting chemicals can cause chemical burns. If none of the above applies, she may have developed a yeast infection. Have a sniff at her paws and see if they seem smellier than usual, if so, it's probably yeast. These infections are very uncomfortable for the dog, consequenty, they lick all the time. The licking keeps the paws moist, which keeps the fungus going. You can get some medicines from your vet to cheaply and easily treat this problem. Don't be surprised if it comes back around from time to time.