I'll just copy and paste the reply (easier then trying to type it out):
Well if it is fine & quiet it could just be broody?? As in nesting behaviour/trying to hatch eggs. Or else it could be egg bound does she know if its been laying in recent days? It could have a egg stuck you can try sitting them in a warm bath if not take it to a vet in the morning for a X-ray see if it has eggs stuck inside??
She assumed that if the chicken was egg bound she would be able to feel an egg/hardness inside, which she can't. Is this right?
Often you can but not always if its high up close to ovary it could be difficult to feel, it can take a bit of practice to feel them sometimes (that's why we X-ray as won't always feel them). Is she certain its not broody?
If broody, would they just not walk like that??
Well yes they will sit for hour/days without moving we pick ours up & take them out to force encourage them to eat & drink which they usually do quickly the high tail it back to the box. Often they won't move if their own free will, can it walk if she takes it out the box??