Doesn't sound like Coccidiosis or a bacteria infection. But watery is not good. Is she getting really thin? How old is she?
You might try this instead for now...add some Apple Cider Vinegar to the water, they can both drink it. 3/4 teaspoon of the cider to 1 quart of water, making a new batch daily. This will do 3 things, 1 it will stimulate her appetite and 2 it will sour up the intestinal tract and 3 it will feed the good bacteria producing more oxygen.
Pathogens don't survive in sour oxygenated conditions, she may have a slight yeast infection somewhere in the tract. Yeast infections are quite common in all poultry. Feed her lots of greens too, especially chopped cabbage or broccoli slaw. Apples are wonderful yeast busters. All of these feed on yeast and aid the immune system. She needs to eat whatever she will eat to keep her healthy and if greens or chopped apples is all she eats until she heals, so be it.