Personally, in the current climate, I'd just bury her and keep quiet. If she was eggbound you should be able to feel the unlaid egg inside her. But as she was fit and healthy only hours previously, then it seems unlikely. It doesn't kill them that fast. You would have noticed her looking uncomfortable first.
Like with all animals - where there's livestock there's deadstock. It's sad in a young animal or bird, but it happens.