This happened to one of my old hens a few years ago. She had the habit of pecking at ice in the winter even though there was always unfrozen water available for her.
On my hen it had broken off nearly as far back as your hen, but there was still a little flesh left underneath where the beak had been. Thankfully the cold weather was in her favor and flies were not an issue. It was however painful, which was really hard to see as she was normally a very outgoing sassy hen.
I debated heavily what to do and ultimately decided to wait it out and see how she did instead of euthanizing her. Chickens are tough and can survive things we never imagine that they could.
It took a few weeks and some babying to heal, but after that she was perfectly fine and back to her old bossy limping (arthritis) beautiful self sporting her stumpy beak with sass.