The white poo could be she was drinking more than she was eating, stress or something else. You really need to try to get something into her. Have your tried handfeeding and maybe taking like a spoon with some water and dipping her beak into the water to stimulate her. Do you have any vitamins and electrolytes to add to the water?
Have your chickens been wormed ever? Did you see any evidence of lice or mites? They are very tiny but if you look at her skin on the back of her neck, vent area or under wings you can see them. They are very tiny so look closely. Lice will attach their eggs to the feather shafts on the back of the neck near the base mostly, around the earlobes and vent area. You will see a white collection of eggs on the shaft of the feather. You really need to start to try and get her well or she might not make it. Check her over real well. See if you can get her to take the water with vitamins and also offer other foods. Scrambled or hard boiled eggs, yogurt anything she likes. I mix chicken feed with water to make it moistened and add vitamins to it when I have a sick one. They do seem to like it and I will hold them on my lap and offer them stuff on a spoon.
Have your chickens been wormed ever? Did you see any evidence of lice or mites? They are very tiny but if you look at her skin on the back of her neck, vent area or under wings you can see them. They are very tiny so look closely. Lice will attach their eggs to the feather shafts on the back of the neck near the base mostly, around the earlobes and vent area. You will see a white collection of eggs on the shaft of the feather. You really need to start to try and get her well or she might not make it. Check her over real well. See if you can get her to take the water with vitamins and also offer other foods. Scrambled or hard boiled eggs, yogurt anything she likes. I mix chicken feed with water to make it moistened and add vitamins to it when I have a sick one. They do seem to like it and I will hold them on my lap and offer them stuff on a spoon.