How old is she? First thing I would do is get a human super B complex tablet or capsule (human ones, regular not time release) and give her one once a day. Deficiencies in B's are not uncommon and can cause symptoms like this. The vitamins may be the fix, if not they won't hurt anything.
Give her a good going over to check for any injuries or wounds hiding in feathers. Check for lice/mites. Get a look at her droppings, see if they are normal. Monitor her crop function, make sure she's eating and drinking normally. Her crop should have food in it when she goes to sleep and then it should be empty in the morning before she has access to food and water again. I would crate her in a wire crate until you have a better idea what's going on so you can monitor her. That can either be in the run where the others can still see her and she can see them, or if she needs to be warmer then inside somewhere. Keeping her with the others makes reintegration easier later.
How many birds do you have, ages, and in how much space?
