Allergies, either to food, or an environmental or contact allergy, usually presents as red and itchy toes and feet. It's very possible that the licking/chewing irritated the feet a bit more than usual and it could turn to self-induced infection if not treated quickly.

I would start by soothing and disinfecting the toes by soaking in diluted chlorhexiderm or betadine in warm water (1 part solution to 10 parts water); if she'll let you, soak the feet for 5 minutes, or at least rinse if you can do that much. Sometimes it's hard to keep them still! The shampoo may help, or could actually cause worse irritation believe it or not.

As long as she is healthy otherwise, you can try some benadryl ("diphenhydramine") OTC as well, at a dose of 1mg per pound of body weight for the itching. (The dose range is 1 to 2 mg, with 1mg being safer and more common, but you can round slightly up or down to get easiest dosing with the tablets or capsules). Capsules are much easier than liquid, as you can hide it in a meatball of anything your dog likes to eat. You'll have to read the package to see how many mg are in each tablet/capsule. Don't repeat the benadryl more than once every 8 hours, and if not helping, then unfortunately a vet will be needed as it may have become infected enough to require oral antibiotics or your dog may need injectable, longer lasting steroid to control the allergies. And don't be fooled by allergies- some are seasonal, but some are food related and can develop over years to a product that has been feed all along. Sometimes a novel protein diet will help (buffalo, venison, duck, rabbit, etc).

Let me know if I can help further, and good luck!

Christine