Must be the warmer weather making the chicks hatch at this time of year. We had 11 hatch outside last week.
Left her a couple of days then brought them all in, for fear of my farm cats. Apparantly a broody hen on her nest is ok with foxes, the hen loses the smell which would attact a fox to her. I have had a few hens sit out anad hatch eggs ok, one was on a railway enbankment, covered in foxes!!
The chicks will be fine with the hen sitting on them - you put your hand under and feel the chicks, if she will let you - they will be lovely and cosy standing under there!!