Is she molting as well? Tucking her head is showing that she doesn’t feel well. If you should lose her, I would have your state vet do a necropsy to find out what was exactly wrong with her. I hope that she comes out of this illness.
Do any of the droppings look like egg matter? If the yellow above isn’t bile, it might be egg yolk. It is good that she is still eating for you. Usually laying disorders are eventually fatal, but some people try antibiotics such as amoxicillin (Aqua Mox found online) or enrofloxacin for pigeons...
Hard to see in the picture, but are the normally white urates in her dropping yellowish? She does have that posture that looks like a hen with internal laying or egg yolk peritonitis.
How old is she and does she normally lay eggs? Check her crop in the early morning before she eats or drinks to see if her crop is emptying overnight. Are her poops looking normal? Pictures are welcome. Is her tail position down? Is her lower belly enlarged? Reproductive disorders are a common...