
It’s so hard with chickens because they hide illness so well and by the time we notice something is off they are too far gone to be able to fix it. In your veterinarian’s defense (I worked at a small animal hospital in my younger years) they see a lot of death. It’s hard to watch animals suffer for longer then they have too usually because the owner wants to exhaust all options of treatment. This vet seen in your bird that she was suffering a lot and wanted to end it for her sake. They do care, a lot more then people think. If they suggested euthanasia even though you were willing to pay for more treatments you know she’s pretty far gone.
If/when she does pass can you send her in to have a necropsy done? I sent a bird in to the state vet that died and I had others sick, best thing I ever did. Found out exactly what it was and saved the rest of the flock.