I had this problem with Bella last year. She had very severe allergies to grass, weeds, and pollen. She chewed her feet until they were ulcerated and bleeding constantly. Benadryl and antiobiotics didn't get weren't helping at all, so the vet biposied the lesions to rule out cancer. The infections eventually went away after about 6 weeks of her being on antiobiotics, though.
The only recommendation I have for you would be to bandage her feet and put an Elizabethan collar on her until the infection clears up. Definitely take her to a vet to rule out anything more serious, though. At the very least, she's probably causing a pretty nasty secondary infection.
Our vet said that chewing on the paws is a food allergy. Have you tried Innova food? It stopped my Jane from chewing on her feet. We recently switched to Merrick and I am praying that she doesn't start with paw chewing again..if she starts,,it's back to the Innova senior. We were giving her cortisone shots before we switched to Inova.
Sounds like an allergy to grass/pollen. My pom has that allergy, I give her solid gold seameal in her food and it's really helped alot. I also wipe down her feet with a baby wipe every day to further remove any pollen in between her toes.
We had that problem too. The benadryl did not work. The vet suggested we put deodrant on his paws the smell and taste should stop them from licking it (however some dogs aquire a taste for this after awhile).
The vet also said you can try a Cayanne pepper mixture, or a sour candy type mixture.
They said it was a complusive disorder. Our dog stoped on his own.