The way she is standing - any bloat/swelling, feeling of fluid in the abdomen?
Photos of the poop? If you have a vet that can check the poop for any signs of worms or coccidiosis overload, that would be great.
Since she is standing all the time, it would seem that she is uncomfortable laying down.She may be suffering from an internal laying/reproductive disorder like Egg Yolk Peritonitis, Ascites, cancer or tumors. Symptoms include lethargy, going off feed, swelling or fluid in the abdomen, penguin stance/standing all the time, lameness, difficulty breathing and sometimes poop that looks like it has egg in it.
If she has swelling in the abdomen that feels like fluid, then sometimes this can be drained to give some relief. Antibiotics usually are not that effective, but may help give supportive care of reproductive orders are caught early enough.
Do the best you can to get her hydrated - if she won't drink, consider tubing fluids into her. Add poultry vitamins if you have them. Once she is hydrated see if she will eat for you.
Keep us posted.