In the meantime, put a urine pad under her to sleep on...It will absorb the moisture and keep it from burning her skin...
Agree that she must be having incontinence issues which would not be unusual at her advanced age. Dogs do not sweat like that so, unless there is some other explanation, it must be incontinence. I too suggest you take her to your Vet for an exam.
What a loving,caring home your little girl has for her to be
with you all these years.
From what you have said,I DO believe she has wet her-
Urinary incontinence can happen in older,spayed female
dogs.The uretha and vagina open in the same area,this
leakage can happen because spayed,older females do
not have hormones after having been spayed.
This could also be caused by a urinary tract infection or
as simple as just being age related since the muscles are
not as tight and they can relax at different times,naps or
while sleeping longer at night,even happens as an older
dogs walk,they are not usually aware of this happening.
It could also be a sign of the start of a problem,I suggest
you take her into your vet,get bloodwork and a urine test
to find out there are no other issues starting or going on