This is more of a reproductive disorder and ascites. Her tail position is down, the belly large, and it can be common to have trouble pooping, or have frequent liquid poops. Hens who look like that are not usually laying. I doubt that she has coccidiosis, but hard to know without testing her droppings. Corid would not hurt her. Coccidiosis is usually seen in young chickens, and they normally build up a tolerance to the coccidia organism in their area.
I would try to keep her comfortable and offer foods that she will take. If she appears to be suffering, I would think about putting her down. Then either do a necropsy yourself and take pictures of your findings, or send her body to your state vet for one.