[Yosemitest]

Depending on how much "Chow" breed she is, it might be best NOT to get another dog.
Just work through it.
Chows are a very "unstable" breed, and through my years in the military, many of my military acquaintances that had them, had problems with them.
Most of them had to be "put down" after, for no reason, they turned and attacked their owners.
If she's old, she's not going to do well with another "puppy", so give her more of your time, in walks, and petting, and holding.
I wish y'all well.

[TASMANIANRED]

We have been wandering on the farm.
I can’t let her go too far, her hips gripe.
She will spend the next several days gimping around.
Shorter walks but more of them.

[Salamander]

Most of the time, the “sudden change” in Chows is due to pain.

Their horrid hocks and knees [or lack thereof, technically] predisposes them to debilitating pain, eventually.

Being extremely stoic dogs, they may not show overt signs of that pain until something really provokes it and they lash out.

My idiot sister thought it would be a great idea to get a “fuzzy little Chow puppy” and then she dumped it on my dog-clueless parents.

He was a SOB to everyone but me because I knew where he hurt when they didn’t even *know* he was hurting.

Then they let a vet give him Rimadyl and it killed him.