I’ve seen a hen get chicks out of a ten feet high hay loft. She flew to the ground and said jump, they did, then bounced up and ran to her. You can help if you wish but my broody hens know when the hatch is over much better than I do. My highest nests are only about 3 feet off the coop floor but I don’t worry about her being able to get the chicks down at all.
One warning. I saw several posts on here about chicks falling out of the nest after hatch before the broody brought them off. I did not understand that at all until it happened to me. Baby chicks that hatch early often like to crawl up on Mama’s back. If she is sitting too close to the edge they may miss the nest when they fall off. I let a hen hatch in a cat litter bucket, about 7-1/2” wide. That nest was about 3 feet off the coop floor. I had to pick several chicks up off of the floor. That nest was just too narrow so it has been retired.
I don’t know what your nest looks like. Most will be OK, especially if it is enclosed and she sets toward the back. At four feet high the size and shape of the nest is the only thing I’d worry about.
When my hens bring their chicks off the nest, they do not go back to those nests. They normally take them to a corner of the coop to sleep on the floor. I’m sure others have had different experiences but mine just don’t take them back to the nest they hatched in, even if it is pretty low to the floor.
I move my broodies and their new hatched chicks to a nest on the floor, the same day they hatch, or the day before. I have had chicks fall to the floor once dried off, and they can't get back to the nest, and the mom won't leave the nest if all the eggs are not hatched. The floor nest is a pet carrier with the door removed.