Wyorp Rock just posted what I was thinking—is she starting to go through a molt? They can act off, distance themselves, eat much less, and it is a time of stress. I have noticed if a chicken starts going downhill, it is usually during a molt or during very cold or very hot weather. If you can talk your vet into doing a fecal float and a gram stain on some fresh droppings, I would do that to rule out enteritis and possible parasites. Mine will let me bring in droppings when I have a dog or cat in for shots or a check-up. Otherwise, I would keep her vent area washed off with warm soapy water, to prevent flystrike and maggots from flies, and offer some scrambled egg, tuna, and canned cat food in moderation to tempt her to eat. My chickens are molting right now, and they always hold out for the goodies.
