@junior67 what breed is she? The broody trait has been bred out of a lot of breeds which means it can be very weak in some birds. Some hens will sit half way through and then quit, and others will reject the chicks when they hatch. Not to scare you or anything, but her breed can help determine if she is really broody or not.
Are you letting her collect a nest? Unless you have a crazy bird like mine, they won't typically sit on nothing.
I would not give her eggs until you know for SURE she is broody. I normally give them eggs at 2-3 days.