Oh man. I wonder if she hatched some chicks and left the nest with them but something took the chicks? Around here, chicks are absolutely not safe from fall to early spring because of the hawks.. they really like to swoop down on the little chicks- they will swoop down even with me standing 10 feet away. Mid spring to late summer, the hawks are up north so the chicks are safe.
She will sit on another round of eggs, wait 1 or 2 more days.. if she still sticks to that nest real good, give her a batch of fresh eggs and take away the old ones. Mark the calendar, so the chicks and hen can be collected before they leave the nest.