If your kitty is otherwise healthy, there is no reason that she shouldn't be able to undergo general anesthesia for a dental procedure. You'll need to have a senior blood panel and urinalysis done first, and maybe an EKG, and the anesthetic/analgesic protocol should be tailored to her needs (eg: IV fluids before and during the dental, blood pressure monitoring, no NSAIDS, etc).
My own geriatric cat has undergone 2 dentals in the last year, and he is 20 yrs old. He did great! (and he has CKD, a heart condition, and diabetes). When it becomes a quality of life issue and starts affecting a cat's food intake, I believe that it would be kinder to euthanize than to not do anything. Painful teeth can be agonizing to live with, and we all know how well cats hide pain.
"To close your eyes will not ease another's pain." ~ Chinese Proverb
“We must not refuse to see with our eyes what they must endure with their bodies.” ~ Gretchen Wyler