Usually its just a sign that her mouth is a little dry, and that her water, if she has some, may need to be changed. If she doesnt have any, shame on you! Get some in there right away! If there is some in there, and its fresh, you may have some residual soap or something in it, and you just may need to dump it and put fresh in there.
If that isnt the problem, then you may wanna go ahead and open her mouth up (gently!) and see if her tongue is hung up on a tooth. if not, and she looks okay, then while the mouth is open, rinse it out with a very small amt of water, (like a table spoonful or so) and see if that helps.
If it doesnt, get her to a vet.