I agree with Dr. Dew, veterinary examination is needed to find out why your dog is chewing at her paws. Until you can get her in, buy an Elizabethan collar at a pet store to prevent her from causing further self trauma to herself.
Has your puppy just started biting her feet, or has this been on-going? If it is a recent occurrence, it she may have burned her feet from walking on concrete or asphalt. If so, you could treat with Previcox, and keep her confined to an area with a soft surface until it heals (about 10-14 days).
Remember, it is difficult at best to try to determine what is wrong with your pet without an examination. The symptoms you describe could be due to a variety of problems. Be sure to take her to your veterinarian for a definitive diagnosis and treatment.