To confirm she is truly broody and worthy of eggs, she needs to spend two consecutive nights on the nest, not roosting in her normal spot. I’ve had hens act broody and even spend one night on the nest but not really be committed. So first make sure she is truly broody.
Read this. It’s mostly about using an incubator but the stuff about storing eggs works for a broody too. Don’t get too hung up on the details. These are guidelines and suggestions, not absolute laws of nature. For example, the article gives a perfect temperature for storing eggs. Most of us don’t follow that exactly because we don’t have a place the perfect temperature and we still do pretty well. Just do the best you reasonably can and you’ll do fine.
Texas A&M Incubation site
http://aggie-horticulture.tamu.edu/...e-Cartwright-Incubating-and-hatching-eggs.pdf
You have a few decisions to make. One is how many eggs. The hen needs to be able to cover all of them. Hens and eggs don’t come all the same size. A bantam may be limited to 4 regular sized eggs while a regular sized hen can cover a bunch. If the eggs are the size she normally lays, I suggest no more than 12. I’ve had hens handle more eggs and chicks than that but 12 is a good number.
Remember about half the chicks will be male. Have a plan for what you are going to do with them.
Start all eggs at the same time. That is real important. They all need to hatch together or you are going to feel real bad when some die in the shell.
You have two basic options, either let her hatch them with the flock or isolate her. People do it both ways, usually successfully. You can have problems either way.
If you let her hatch with the flock, mark all the eggs so you can tell which ones belong under her. I put a couple of circles on with a Sharpie, one the long way and one the short so I can tell at a glance which ones belong. You’ll need to check under her daily and remove any eggs that show up that don’t belong. As long as you remove them daily, those are still good to eat.
If you isolate her, fix up a predator-proof area where you can lock her in there and not let her out or any other chicken in. The area needs a nest, food and water, and enough room for her to get off the nest and go poop. It helps if the nest is kind of dark. That seems to soothe them. Move her at night with as little light and commotion as you can manage. Give her a couple of fake eggs like golf balls for the first couple of nights so you don’t risk the real eggs in case she breaks from being broody because of the move.
Some people feel real strong about moving her and others about not moving her. People do it both ways. You are dealing with living animals so sometimes things don’t work out the way you want, but they usually work out.
Don’t worry about your rooster. You are dealing with living animals so you never can tell what will actually happen, but a dominant rooster is much more likely to help a broody with her chicks than harm them. If you have any problems with any of them, I suspect it will be a hen, not the rooster. The only time I’ve ever had a problem with another hen was when she went broody a few days before the eggs were to hatch and she fought the original broody, trying to take over the nest. Some eggs were damaged. Boy was I mad!
I’ve never had a problem with a non-broody hen messing with a broody. When the hormones that cause broodiness get flowing in more than one female at the same time is when I’ve had problems.
Enough typing. Hopefully you’ll get something out of this to help you. Good luck!