Go ahead and treat with Corid. If coccidiosis is the problem, you should see a difference n a day o two. If that's not the problem, the Corid won't hurt her. It's a benign treatment.
To get her drinking, lay some water/electrolytes along her beak with an eyedropper. She'll swallow reflexively. If you're worried about eating, give her some sugar water. That should hold her until the Corid kicks in and she feels more like eating.
