If a vet is possible, take her in tomorrow. Give her water with vitamins and electrolytes, such as SaveAChick, or some Poultry Nutridrench. Use a dropper if necessary. Check her skin around the vent and elsewhere for signs of lice or mites (tiny bugs, white or dark egg larvae.) Take in a few samples offresh droppings for a fecal test to your vet. Give her some soft egg, tuna, or wet feed. Make sure she isnot cold or chilled.
Also, how old is she? Could she be getting ready for a molt, or has she recently been broody?