Maybe put "place holders" under her until Saturday? When you get her off the nest on Saturday to take her walk and poop, you can switch them out.
I have a black australorp who went broody on the 7th. It took a few days, but we got into a routine. She's in a 3x6 coop by herself, with a small bowl of water, sitting on 8 fertilized eggs. Every morning when I go outside for animal chores, I open her door first, sprinkle some sweet feed or special treats for her at the corner of her nest box. She eats them while I tend to the goats (leaving her door open). I turn around a few moments later, and she's out, scratching in the yard, drinking lots of water, and making huge piles of poo. She's usually out about 10 minutes, and doesn't mind if I go up to her nest, count eggs, refill her water so if I needed to add more eggs or do a switch off, that would be a good time to do it.
Of course, you know that making her get off the nest a little bit every day will help keep the nest clean (no poo), and keep her from fading away (watch the comb color).
Mrs. K: probably, yes. Chickens can't count.
Sorry I rambled. It's kinda late.