She might be broody or she might not. I’ve had hens show practically all the signs of being broody yet not kick over into full broody mode. They are living animals and don’t all read from the same book. My test to see if a hen is truly broody is that she needs to spend two consecutive nights on the nest instead of roosting in her normal place. If she does that, then I am willing to give her eggs to hatch.
If you hatch eggs, you can count on some males. Do you have a plan for that?
The odds are tremendously good that all eggs are fertile. You can crack some eggs and look for the bull’s eye if you want,
https://www.backyardchickens.com/t/16008/how-to-tell-a-fertile-vs-infertile-egg-pictures but in your case I would not worry. If the eggs you crack are fertile, then the ones you don’t crack should be too.
You can either isolate the hen or let her hatch with the flock if you wish. There are benefits, disadvantages, and risks with any way you do it. Again, living animals don’t come with guarantees of how they will behave. If you let her hatch with the flock save up all the eggs you want her to hatch, mark them (I use a black sharpie), and start them all at the same time. Then every day after the others have finished laying, remove any eggs that don’t belong. As long as you remove them every day you can still use them.
If you isolate her, fix up a predator-proof pen, give her a nest, food, water, and some room to go poop. A broody hen knows to not pop in her nest but she doesn’t know to not poop in her food or water so you might be doing some cleaning. I suggest trying to make the nest fairly dark. That seems to help them accept the move. Then move the hen at night using as little light and commotion as possible. Have fake or sacrificial eggs in the nest at first until you see that she has accepted the move, then give her the real eggs. Leave her locked in there until the eggs hatch. That way she does not go back to her old nest and other hens do not get in there to lay in her nest.
There are a lot of variations on all this, we all do things differently. I wish you luck!
