Spot looks like fowl pox to me.
Virus carried by mosquitoes, should clear up in a few weeks, don’t mess with it or it could spread.

If you don’t want her to hatch out chicks, IMO it’s best to break her broodiness promptly.
My experience goes about like this: After her setting for 3 days and nights in the nest (or as soon as I know they are broody), I put her in a wire dog crate (24″L x 18″W x 21″H) with smaller wire on the bottom but no bedding, set up on a couple of 4×4’s right in the coop or run with feed and water.

I used to let them out a couple times a day, but now just once a day in the evening(you don’t have to) 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. Or take her out of crate daily very near roosting time(30-60 mins) if she goes to roost great, if she goes to nest put her back in crate.

Tho not necessary a chunk of 2×4 for a ‘roost’ was added to crate floor after pic was taken.

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