
Has she been checked elsewhere? Soli used to lick her front paws/wrists when she was in need of chiropractic adjustment, it was misalignment elsewhere causing referred pain to her feet. As her arthritis got really, really bad towards the end she did it more too.
Also, Saffi has just started doing it and I think it's arthritis in her case - she has it very badly elsewhere but I think it's starting up in her elbows now and again, it's referred pain in her feet making her lick.