There are a lot of different signs that a hen might be broody, but I’ve had hens give about all the signs and not be worthy of eggs to hatch. The hormones that make them truly broody are almost there but not quite.
My test of whether or not a hen is truly broody and worthy of eggs is that she must spend two consecutive nights on the nest instead of roosting in her normal spot. One night on the nest is not enough. I’ve had several spend one night and no more. They will get off the nest for a bit during the day to eat, drink, and go poop. That’s normal. It has to be two consecutive nights on the nest.