Becareful of the teeth.My Tea Cup Chuhuahua had a bad tooth but no issues.They had to pull two of them .She is smaller than yours.But they are nitorious for bad teeth!!!Also eye problems.
Are there any updates on your mother's dog's condition? How is she?
I hadn't thought about it at the time but even though it's cold out and there are no bees, there ARE spiders INSIDE the house and perhaps if it's not a tooth the culprit could be a spider?
Ghilly
She may have an abscessed tooth or something stuck down in the gum alongside a tooth. Is she pawing at her mouth at all or continually licking her lips and acting uncomfortable? Swelling is a sign that there is absolutely something wrong and most swelling is accompanied by some degree of pain, so in light of this, I would get her to an emergency vet this afternoon so that she doesn't have to be in a lot of discomfort until your regular vet opens in the morning. Dogs and cats are very stoic and can hide TREMENDOUS amounts of pain, so just because she's not whimpering of crying outright doesn't mean she's not miserable. Their instincts tell them that to show sickness or weakness makes them prey to other animals so usually by the time they DO show us that they don't feel well, they are really quite sick. Please post back and let us know what the vet said.
Ghilly