She might be broody, or in a false broody cycle. Is she setting on eggs or just the empty nest? If she's setting on an empty nest or infertile eggs, she will break the broody cycle herself eventually, but if you want to speed up the process, what we usually do is take the hen off the nest and put her in a pen so she can't get back to the nest. And then we feed her up if we need to, sometimes they lose weight from doing that, so we give her special food and treats, etc. After three days or so, she's back to normal, and we can let her out, and she won't return to the nest for long periods like that. Do you have a rooster? If so, and she's setting on eggs and you want the chicks, just leave her alone, because the chances are good that the eggs will be fertile. The chicks will take 21 days, on an average with a bit of variation, to hatch. The hen doesn't need help, she will keep herself supplied with food and water from the resources you are providing. She will set for long periods but will get off the nest long enough to eat, drink, relieve herself, and stretch..you just might not see her doing that.