To me, your hen's poo indicated being over-heated and/or illness. Broody poo is big, thick, and especially large in content. Thin and runny poo is not a good sign. You had her high in the rafters, is it possible she was too warm in that area?
Also, I keep hearing it repeated that hens can brood themselves to death as if this is a natural occurrence and something that we poultry managers need to regularly protect our brooding hens from. However, It has been my experience that a healthy hen does not starve herself to death while brooding. Hens are designed to brood and withstand brooding. Unless a hen has developed a worm overload, external parasites, or has very poor food/water support during the brood, (all things to manage and maintain during the brood), she will not succumb to the ills of brooding in and of itself.