My go-to signs of a broody:
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.
You'll need to decide if you
want her to hatch out some chicks, and how you will 'manage' it.
-Do you have, or can you get, some fertile eggs?
-Do you have the space needed? Both for more chickens and she may need to be separated by wire from the rest of the flock.
-Do you have a plan on what to do with the inevitable males? Rehome, butcher, keep in separate 'bachelor pad'?
If you decide to let her hatch out some fertile eggs, this is a great thread for reference and to ask questions.
It's a long one but just start reading the first few pages, then browse thru some more at random.
https://www.backyardchickens.com/threads/broody-hen-thread.496101/