There is a nice article in the Learning Center about broodys and how you can discourage them if you want to https://www.backyardchickens.com/a/encouraging-or-discouraging-broodiness-in-your-hens I like using a separate cage like what they call a broody breaker, it usually works really well. I usually just use a wire dog crate, size doesn't really matter, the bottom wire spacing is usually around 1x4"... you want it really uncomfortable for her to stand/sit on. I put a couple of perches in there and hang small food/water dishes on the sides so they can't stand or sit in them. Put the crate out in the open, I prefer to put them in the middle of the barn aisle or coop so there is a lot of activity and light... you want the hen to be bothered. They don't like to walk on the wire so they spend pretty much all the time on the perches, that works pretty well for most of them. I've never tried it, but some people have mentioned putting a small fan under them to cool them off even more.