I think, and it's just a hunch and I have no way of knowing of course, that this is more than just a stuck egg. The closed eyes tell me this hen is on the brink. That she's in the nest also tells me it's related to egg laying.
There is a condition called hypocalcemia where calcium levels are critically low and when a hen starts to lay an egg in this condition, when the egg reaches the shell gland to get a shell built, it draws the last remaining stores of calcium out of the blood stream and the shock of this can stop the heart.
The closed eyes and being in the nest are two clues that point to a possible life ending crisis unless intervention occurs immediately.
If I'm wrong, which is certainly possible, no harm done, and these measures may revive her and help her lay an egg that may be stuck.
There is a condition called hypocalcemia where calcium levels are critically low and when a hen starts to lay an egg in this condition, when the egg reaches the shell gland to get a shell built, it draws the last remaining stores of calcium out of the blood stream and the shock of this can stop the heart.
The closed eyes and being in the nest are two clues that point to a possible life ending crisis unless intervention occurs immediately.
If I'm wrong, which is certainly possible, no harm done, and these measures may revive her and help her lay an egg that may be stuck.