I still cry whenever anything reminds me of Moses, my first dog. (And probably all my other dogs and cats too, but especially that first one.)
I usually try to have two dogs, one a few years older than the other, so that if one dies you still have one with whom you are already bonded. It takes some years to develop the depth of bond which it hurts so much to lose, so a new puppy is a great distraction, but in some ways can make it more apparent just what one has lost.
The other reason for having other pets / livestock is that caring for them makes you get up and do stuff, and that really helps.
I'm glad to hear that your niece is starting to heal