Very Sick Chicken
Welcome to BYC. Start some electrolytes with vitamins in her water, and try feeding some with dipping her beak or using a dropper to drop some into her beak. If you can't get that, you can use Pedialyte, Gatorade, or put a small pinch or salt and tsp of sugar in a liter of water. She may be dehydrated weak from not eating. Has she been wormed recently, or have you seen any coccidiosis in your flock? Have you added any new birds recently? Make sure that she is kept warm, and take in some fresh droppings to the vet.