This is only "advice" and what I would do. I would seperate this one, be sure she has clean, warm water and clean food. I would try to get her to drink but touching her beak into the water to see if that would stimulate her. If it does, that would be a good sign. I would also try to feed her some yogurt with a bit of feed mixed in, again dipping her beak into the yogurt to try and stimulate her. I would try to then let her be for a bit and see if she just needs some peaceful sleeping, it is tough on them when they arent feeling their best and the others are climbing all over them,etc. After giving her a bit of warm, quiet rest, and hopefully she eats/drinks, I would reevaluate and see what I think then.
Good luck!