Not sure if its a myth. But i heard that once you do their anal glands for them, you will always have to do it for them. Which seems to be true of the dogs i know.
My parents beagle had an infected anal glad. But you could tell as she was rubbing rear on the floor and kept licking it. She went on medication for it and it cleared it right up.
I would probably take her into the Vets to be sure its not infected or anything to be on the safe side! They can advice you from there.