The thin shell, isolation, not eating but drinking a lot of water are signs of a problem. I would examine her vent and belly closely.
How old is she?
If she doesn't snap out of it within a day or two:
I'd isolate bird in a wire cage within the coop for a day or two....so you can closely monitor her intake of food and water, crop function(checking at night and in morning before providing more feed), and her poops. Feel her abdomen for squishy or hard
swelling.
Best to put crate right in coop or run so bird is still 'with' the flock.
I like to use a
fold-able wire dog crate (24"L x 18"W x 21"H) with smaller mesh(1x2) on bottom of crate under tray.
Then you can put tray
underneath crate to better observe droppings without it being stepped in. If smaller mesh is carefully installed, tray can still be used inside crate.