Is this only a recent behavior? Has she been pooping further away up to now? If so, what has changed in her environment to make this change in her behavior?
How big is her enclosure? Sometimes it helps to put the food & water on the far side of the pen so they have to walk a bit to get to it. Perhaps it's getting colder where you are & she doesn't want to leave the eggs long enough to poop.
Each broody hen comes with her own component of skills, some do everything well, some are prone to some unwise behaviors. Since it's so close to hatch time I wouldn't lift her off the nest any more, just let her be. She may not need food or water or to poop until the chicks hatch, so if she doesn't get off the nest on her own don't worry.
If she does poop in the nest just try to get it out without disturbing the hen. If it's the typical big firm smelly bomb that broodies make you could -- if you dare-- pick it up with a gloved hand. As long as it's not wet or runny it shouldn't hurt the chicks, they'll encounter a lot of her poop while they grow.