I've been using hospice with palliative care for some years now, and have seen my animals through a peaceful, natural passing.
I wondered if I should 'interfere' during such a personal and intense time. In both cases, I suspected that the friends would not be disturbed by suggesting that they look into hospice and natural death. I considered the animals' needs first, and the humans' alongside...
In both cases, they were grateful for being introduced to natural death for their animals. (whew) The first friend found the dying process of her cat to be profoundly moving and were happy to be with her as she made her way into spirit.
The second friend has a dog who is still with us, but close to her last days. Both friends love their animals deeply, and want the best for them. My second friend had the dog, and though I know the dying process to be the same for all beings, I'd never gone through it with a dog. I gave him (and the first friend) a copy of Gail Pope, founder of BrightHaven sanctuary and hospice, a copy of her booklet, Soar My Butterfly, an invaluable week by week, day by day, and last minutes guide to what to expect and what to do, if anything. Highly recommended!! He is with her as she slows down, sleeps most of the time, enjoys his being by her side, and has pretty much stopped eating. She is in no pain, though he has pain medication on hand in case it's needed. It is a good time for them both.