the glands fill daily with fluid. Usually when your pup poops a good hard poop it empties the glands (not ACTUALLY glands- sacks) - layla had LARGE anal glade issues, hence i know this
) So if the poop is soft- nothing empties the sack and the fluid starts to thicken which makes it harder to empty the next next time... they feel the pressure in their bum and rub it against the floor. Either a vet or a groomer can empty them. If it is a constant problem- try adding fibre to her diet- something like metamucil is great or just give a few baby carrots or some apple without the skin- or even a bran cereal as a "treat"