Being broody isn't good for a hen because she is sitting on the nest all day instead of bing out and about, feeding and taking exercise. If she is actually sitting on a fertile clutch that she can eventually hatch, then there are advantages of course, but if this isn't going to happen she'll just go deeper and deeper into a hormonal state, become zombie-like, lose weight from not feeding, lose feathers on her chest as she develops a brood patch, and of course will not be laying whilst she's afflicted. Also, if the broodiness isn't promptly corrected, she will take much longer to get over it and it'll be more likely to recur.
To get her hormones back to normal as quickly as possible, she needs to be forced to get out in the sunlight and nt be allowed to go into a dark nestbox or to snuggle down into soft bedding. And definitely no eggs for her to sit on, real or china! or My Marigold, a purebred Buff Sussex, goes broody repeatedly in the summer, I think it was four times last year, thought as Chris says this is much less likely in a hybrid. Each time, I was alert for the first signs of her wanting to stay in the nestbox, and I removed her to a bare, fenced- off corner of the run where she could see the others but not get back in the coop. I left her there at night as well as in the day and after three days I let her out and watched to see what happened. If she didn't go back in the nestbox I knew she was cured, but if she did, she went back into her 'bedroom' for another day if two. If I hadn't acted promptly it would take much longer for her to get over it as her hormones would be much more deeply affected.
It then takes sbout 3 weeks before a hen starts to lay again - I suppose that's because it takes 21 days for an egg to form and a hen goes broody once she has laid a clutch and possibly at that point the supply of eggs is shut off? So the sooner she gets back to normal, the better I think.
Some people shut a broody up in a dog crate but I think it's kinder, and just as effective, to confine her in the run where she isn't isolated from the others and can walk about and complain about her cruel treatment. Thus probably helps her to keep fitter and whilst she's moaning she isn't sitting down and getting her chest hot. The main factor is getting her out in bright light, though, as thus will stimulate egglaying hormones rather than broody ones.
