Photo of her poop would may be helpful.
It's good that she is drinking. Check her crop first thing in the morning before she eats/drinks to see if it has emptied. The crop is on the right side of the breast, you should be able to run your hand down that side and feel the crop if it has food in it.
If the crop is not empty (before she eats/drinks) then you have a crop problem.
I would still continue with the Corid as suggested.
Not being nitpicky here. In your photo your water station is on the ground and to me, the water level in the cup looks a bit low. (I do see water in the top part, I'm not saying they don't have water). Sometime those gravity waterers don't glug out like they should, they get bedding or debris stuck in them, they can be a pain.
I would set the water station on a brick, block of wood - make it about chest high for them to drink out of, it will stay a little cleaner that way to (sometimes

)
Her drinking like crazy makes me think she is dehydrated or could possibly have a crop issue. Do they have a source of grit available free choice?
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https://the-chicken-chick.com/chicken-anatomy-crop-impacted-crop-sour/