This is so so sad! I am SO very sorry for you.
Who's dog was it? If not yours have you reported it as it obviously came onto your property?!
Luckily ( hoping not to temp fate here ) none of my girls have ever suffered an attack or injury. Although my quail have, some terrible wounds beyond help. The ones that are help able, I worry myself silly over. First for infection, second for shock. I always clean the wound thoroughly, put them on heat separate from any other bird. Make sure they are drinking then eating. I tend to them daily, cleaning wounds, keeping their area clean. That's exhausting ( more mentally and emotionally that any thing else )
I understand what you mean by the smell though, years back one of our cats ( theres a reason for this story )
Lola went missing. We found her walking the dog around 8 days later, her collar had somehow got pushed over her paw and cut deeply into her pit/under arm. The smell was just aweful!! I honestly thought Maggots, it smelt like a rotting dead animal.
We rushed her to the vets as soon as we found her ( around 9 at night this was )
They put her on fluids as it was middle of summer. She went to surgery the following morning and had some of the infected flesh removed. They couldn't stitch due to where the wound was. It took about 4 weeks ( two of which with this horrendous smell ) she wasn't allowed out for pbvious reasons. Had to clean the wound several times a day. With your chook ( bless her heart ) the removal of infected skin seems unlikely or possible given how wide it is. I'd keep a very close eye on it, if it seems to be getting worse, don't hesitate in taking her back to the vet! I'd also see about pain relief, she must be in so much discomfort, probably why she's lost her appetite couple with infection and shock.
I really do hope she recovers, keep us posted?
And definitely if the dog was not yours, report it! If it can do this to chickens, what else can it hurt? My dogs 1 jackrussell 2 chihuahuas are not allowed to bother any other pets be it chickens, cats, rabbits or birds. They pay no attention what so ever, been around them since pups.
Just so sorry for you, can't imagine how aweful it must be.