{{{Cash}}}, don't feel like you have to hold yourself up to anyone else's example when it comes to the dog -- it is a quality of life issue, for them as well as you, and old age hits animals hard and fast. All you can ever do is give her the best care you can manage for as long as you can manage it.
(The same give-her-the-best-care-you-can business goes for you too, incidentally. Seems like you need it right now.)