Sick Chicken

Last night one of my Blue Cochin pullets was drinking a lot of water. She sat next to the water pan and drank very frequently. She was hanging out near us where she usually doesn't get very close. This morning she was roosting on the side of the coop, wings drooping, shaking, lethargic, and diarrhea. I picked her up and petted her (which is strange because she doesn't usually get close enough) and sat her next to the water. I'm very concerned for her. What should I do?