I had a hen hatch eggs in November a couple years ago. It wasn't too cold at first but after about 5 days it dropped to 10F. I hung a heat lamp over the food and water across the coop from the nest. I wanted them to be warm enough to eat and drink. Otherwise they'd have to stay in the nest with...
Good info.
I have another point of view for the OP. If you don't have separate quarters in which to raise up the chicks to full size before integrating, it would be best not to segregate the broody and chicks. She will protect them from the flock with ferocity right now. By the time she weans...
I'd just wait till she comes off the nest on her own. When she does, grab any unhatched eggs and move them to an incubator if you have one. Get your cage ready and at nightfall, move her and the brood.
I'm guessing they're close to hatching. They're completely dark inside when ready to hatch. No feet or wings visible.
Do you have a means of securing her where she is?
A hen won't continue to lay eggs once she starts setting. See if she is out and about for more than 20 minutes or so a day. If so, she's not broody. Does she sleep in the coop? = not broody
If she is broody, you'll have to move her and the eggs to a nest in a safe place. Predators are...