They don't need eggs to be broody.
First make sure she is broody, here are my go-to signs:
Is she on nest most the day
and all night?
When you pull her out of nest and put her on the ground, does she flatten right back out into a fluffy screeching pancake?
Does she walk around making a low cluckcluckcluckcluckcluck(ticking bomb) sound on her way back to the nest?
If so, then she is probably broody and you'll have to decide how to manage it.
If you don't want her to hatch out chicks, IMO it's best to break her broodiness promptly.
the longer you wait to break her, the longer it might take.
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 4x4's right in the coop or run with feed and water.
I let 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 2x4 for a 'roost' was added to crate floor after pic was taken.
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