How is she otherwise? Alert, lethargic? Is she eating and drinking? How are her poops? How old, anything changed recently? Any new additions to the flock? How old is she? How is the rest of the flock doing?
Thank you for your prompt response. She is 3 years and five months. No change, she just woke up 4 days ago not wanting to leave the coup. She is barely eating and drinking, alert, she pooped only once this morning. I brought her in today, trying to keep her hydrated by spooning her the water. The rest of the flock (6 hens) are all healthy so far.
Given her age, and that she’s not eating or drinking, culling her might be the kindest option, or take her to a vet to have her euthanized. Sounds like she is suffering, and chances are that she won’t recover.
Maybe someone with experience with sick chickens can give you better advice. Check for curable things like impacted crop, egg binding.