Her signs are non-specific to any sort of disease, so it's hard to suggest what might be going on. Performing a physical examination on her may prove useful in the identification of her problem.
This morning, how does her crop feel? Do you have any pictures of her feces, how are they looking? Could you post a picture with a whole-body?
Reproductive problems such as EYP, or salpingitis are common in hens two years or older. Could you gently palpate her abdominal area, does that feel bloated or swollen at all? Hard, watery, firm, distended? If her abdominal area feels a little hard, and bloated, you can check for an egg by sticking a lubed up finger into her vent area.
If she's not eating or drinking much, try offering mashed scrambled eggs, or soupy feed, and see if she'll take to that. Weighing her to determine when, and if tube feeding will be needed to maintain hydration and nutritional status would be a precautious measure. Sick birds generally don't eat much food so have very little "fuel" to keep their body warm, considering that, you may keep the temperature a little higher where you're keeping her.