Dogs seem to always be a threat to chickens.
I'm glad you were able to fix the problem.
I'm sorry about the loss of your dog, it is very hard
You are doing good, don't beat yourself up. You'll never know exactly how the beak was broken.
I'm glad she is able to eat!
I would just keep an eye on the nostrils to make sure they don't get clogged with feed.
I hope she heals just fine.
Keep us updated!
I can't advise on what caused it.
Poor thing.
The biggest thing I think will be that her lower beak is going to be longer, I think the top will eventually fall off. You could try giving her wet pellets or mash in a deeper bowl so she can scoop her food. If not you will have to try to tube feed...