Antonio Hache wrote:She moves towards the water or food, with lots of effort, and once she got what she wanted, she lays face up again
No idea what could be causing it, but that is indeed very strange behavior, which to me hints that she is feeling very unwell. You said she was limping before - maybe this is the way that she's found to keep pressure completely off an injury?
You already separated her, so I assume that you placed her food and water quite close, to make healing easier on her. If she were my chicken, I would probably bring her inside for extra close monitoring. But beyond that... I'd be doing the same as you, posting online wherever I could, because that is truly bizarre!