First, my disclaimer. Each chicken is an individual. It is always possible you get one that has its instincts screwed up. It sounds like Aart had one of those and managed to work through it. I don't know if your hen has issues or is like the vast majority of broody hens.
Broody hens should come off the nest on their own to eat, drink, and poop. They should know to not poop in their nest and mess up their eggs. Sounds like yours has that part. I've seen broody hens come off the nest twice a day and stay off for more than an hour each time. I've seen a broody come off the nest once a day for only 15 minutes before she went back. Sometimes I never see a hen off her nest but since she is not pooping in her nest I assume she is coming off. They all had good hatches. Part of the broody instinct is to hide a nest. That might include not letting you see her when she is broody. They can be really sneaky.
If another chicken can get to her nest it is a real good idea to mark the eggs she has and check under her once a day to check for new eggs. There are different reasons for that. I check my broody hens every day after the others have laid. I have never had a broody hen break from being broody by me taking her off once she has committed to being a full time broody. Not all hens immediately switch over to being a full time broody. Taking her off the nest might break her. But these are not committed enough to being trusted with eggs anyway. She could stop at any time. If yours has been there 4 days, I would not worry about that.
When you take a broody hen off her nest she often squats on the ground for a while. Then she either moves back on her nest or takes ff for food, water, to poop, or maybe take a dust bath. She goes back on her nest when she finishes with all that. There is nothing wrong with taking her off the nest when you check for new eggs and setting her on the ground. If she is not pooping in the nest she is coming off anyway and you are not seeing her.
I do not put food or water in the nest. Some people do for their own reasons. My reasons not to are that I don't want to spilled water to soak the nest and I don't want the food to attract rodents or other predators to her nest. Do as you wish on that.
Hens have always been laying eggs and hatching chicks in all kinds of strange places. Some man-made nests are pretty poor for a broody hen. I don't see anything wrong with that location. My criteria concerns how safe is that area from predators. That's the only reason I might even consider moving her.
The vast majority of broody hens know more about this by instinct than I ever will. I find that the less I interfere the less harm I do.
Good luck!!!
