Separate her from other chickens immediately. Her lower belly below her vent has been pecked open and cannibalized. Have you seen any vent pecking or bullying? Is there any way she could have been hurt by a predator? I would apply saline, weak Betadine or chlorhexidene to the wound. Then apply plain Neosporin antibiotic ointment after cleaning the wound twice a day. Offer her some sugar water or electrolytes up to her beak for shock. Later if ahe is drinking, offer some watery chicken feed and bits of cooked egg. Time will tell if she will recover because she could suffer infection.
