When I use an incubator, the chicks almost always hatch on day 21, or day 22 at the latest. But when I let a broody hen sit on some eggs, they didn't hatch till day 25! Birds aren't as precise as incubators and remember everytime they get off the nest to eat and drink and poop, the eggs will cool down slightly. So there's more of a chance that they'll hatch late, compared with incubator eggs that have beenm kept at a steady temp. Leave her for a few more days and try not to worry too much. Sounds like her eggs are just about ready to hatch!