Hi no empty nest,
I too have had a few broody hens sit on some explosive stinkers. I understand why you don't want to candle at this point. I have also learned that when a hen kicks out an egg, she knows it's bad. I recommend tossing it instead of attempting to put it back under her, it's probably a stinker in the making.
I would leave the hen alone. If other hens laid in her nest while she was sitting, she will continue to sit for another few days up to a week to hatch more of the chicks out. Keep a close eye on the lone hatched chick. I would place crumbles and water in the brooder so the lone chick can eat while it waits on the other's to hatch. Be careful that the water container is not too deep to prevent the newly hatched chicks from drowning. Try using a dish that is only an inch or two deep. Some people place rounded stones in the water container to prevent drowning.
The hen will at some point make a choice between taking care of the hatchlings and abandoning the rest of the eggs. She may not get off the nest to care for the chick and continuing to sit on the eggs jeopardizing the chick or she may abandon the eggs to care for the chick. I have seen it go both ways. In the case that she abandons the nest, you can opt to complete the hatch in an incubator or under another broody hen. If you don't have an incubator, you can make a simple incubator by placing the eggs into a box with the lid and placing it under a lamp trying to reach a temp of between 99 and 100 degrees. (you can find instructions about how to do this online or even on another BYC forum). The other option is to toss the eggs after you are certain the hen is no longer sitting. She can leave the nest for a period of time to eat and drink and poo without harming the other eggs. As long as she comes back to sit, she has not abandoned them.
If she abandons the chick to complete the rest of the hatch, you can take the chick and put it in a brooder with a heat lamp making sure it's at 95 degrees and reducing it by 5 degrees each week, or the chick may not survive. I wouldn't rush at intervening, if you said she has left the nest to care for the chick, she may be able to do both for another couple of days without any problems to either chick or eggs.
If you intervene and take the chick, she may take the chick back after the others hatch. You can just try placing the older chick back in with her flock, but watch closely, sometimes they will be reunited with no issues, other times, she will peck at the chick to go away, at which time, I would leave the chick a while longer. Many times the hen will accept the chick back in with the rest of her brood. It just depends on the hen. If all else fails and you end up keeping the chick separated, it's always a good idea to raise it with another chick. They need a flock mate.
Happy Hatching!