She does appear sick. Her tail is held down. I would worry that she has a reproductive disorder. Those are common in hens over 2-3. Keep an eye on her crop, to make sure that it empties by early morning. If not, her crop may not be emptying. A hard or doughy crop in early morning may be impacted crop, while a puffy balloon-like crop could be a sour crop, especially if there is a bad or sour odor from her beak when the crop is pressed. Crop disorders can be on their own, but they can sometimes accompany reproductive disorders as well. It would be good to know if she is laying. Separating her inna dog crate with food and water for a day or two, but also keeping her with her flock for company would be a good way to do that. It would not hurt to worm her with Valbazen 1/2 ml orally, and repeated in 10 days. SafeGuard Liquid Goat Wormer can also be used at 1/4 ml per pound given the same way or for 5 straight days. Worms sometime can cause issues.