I have loads of broodys and each and everyone came back into lay by the time the chicks were around 5 weeks old. Yes, she will quit laying for the 3 weeks she is sitting and again, until the chicks are old enough for the most part not to need to be under her.If a hen has been broody for a while now will she every lay again? I've heard yes and no. I don't want to hatch any chicks so if she is not going to lay anymore I'm going to sell her.
If you don't want her to hatch out chicks, break her of her broodiness...sooner the better.
My experience went like this: After her setting for 3 days and nights in the nest, I put her in a wire dog crate with smaller wire on the bottom but no bedding, set up on a couple of 4x4's right in the coop and I would feed her some crumble a couple times a day.
I let her out a couple times a day and she would go out into the run, drop a huge turd, race around running, take a vigorous dust bath then head back to the nest... at which point I put her back in the crate. Each time her outings would lengthen a bit, eating, drinking and scratching more and on the 3rd afternoon she stayed out of the nest and went to roost that evening...event over, back to normal tho she didn't lay for another week or two.
Water nipple bottle added after pic was taken.