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.