We have 2 dogs. A lurcher 12 years old & a recently acquired ex racing greyhound same size very timid. The lurcher we have had for 10 years has always been difficult to feed but never as bad as now , only about half what she should. The greyhound is the opposite she eats her alloted amount + & would eat much more .She is 4 year old. They get 2 walks a day ,one short one with me as I am disabled somewhat ,& one long one with my wife who though mid 70s too is quite agile still. We regularly see vet for reassurance as much as anything & both are in good health

What do you feed her?
She may have sore teeth and gums. Try various ways of moistening small size kibble with broth and soft dog food. Make small batches so you don't have to throw it out.

Lift her lips and examine her teeth and gums carefully for signs of decay and infection. Also check the color of her gums and tongue, which should be pink. Anything unusual, take her to the vet. Even a hole in the tongue from a sharp tooth puncturing it can hurt, but in old age it's usually tooth decay.