I can't really suggest an approach without seeing the wound or observing her condition. I'd get some antibiotic ointment into the wound, keep her quiet and warm. She may not have an interest in food but keep water nearby.
Humane euthanasia may be the best course of action.
This indicates at least one broken bone.
Chickens have tiny lungs that are flush with the ribs and backbone. Their respiratory system is complex with air sacs and hollow bones carrying air to and from the lungs.
It is possible the broken hollow bone won't heal properly and her respiratory system...