(Sorry....posted too quickly and can't edit my post.)
Whatever you see or don't see, she is showing you she feels unwell, so your duty to her is to take her for a medical check.
Hi David,
Your girl is probably feeling unwell. None of us here can diagnose what may be wrong. She really needs to see a vet. There are so many things this could be, and she needs a professional to take a look at her.
Does she have any other symptoms? Does she have a bit of a swollen belly? Is she peeing/pooping just right and normally? Is she eating and sleeping well? Is she drinking normally? What colour are her gums? Are they pink and healthy, or pale?
By the way -if she has pale gums, she needs to see the vet VERY URGENTLY.
If her gums are black, and you can't tell, take a look at the skin just inside her eyelid. Pull down her bottom eyelid slightly and take a look there.