The first thing that you can try is drying their feet when they go outside. Dogs often get used to licking their feet to clean them after going to potty. If you dry the feet well, you might be able to stop this behavior.
You can also try a little trick that I learned a couple of years ago. I have a poodle who is a terrible licker. She will do it all night and keep everyone up with her licking and slurping. So - I started a retraining process with her. I started out by snapping my fingers at her every time she did it. If this worked to distract her, great. It usually did not. So, I moved on to step two. I snapped my fingers loudly and then lobbed a small, light weight, beanie baby at her. I tossed it gently so I would not hurt her but would land right by her nose. So - snap - wait a few seconds - throw the beanie baby. Pretty soon, I could just snap my fingers and she would stop the licking. That started two years ago and it still works for me.
I would try drying the feet and a retraining process that will work for you. If that does not help, you will want to discuss allergies with your vet.
Many dogs get a great deal of relief from a low allergy diet that your vet can prescribe. You also want to have the vet check for a secondary or bacterial fungal infection that might be causing pain between the toes.
Also, this can be an anxious movement on her part. There is a great cure for anxiety that is all natural. It's called homeopet (www.homeopet.com) and it's a great way to relieve anxiety in pets and this might, in turn, help with the licking if it's caused by an obsessive disorder.
I hope this helps!
Let me know if you still have questions.
