Has she been setting eggs in the last few days/weeks? If so, you might wait until night time, then, in the dark, remove the eggs one at a time and substitute a chick for the egg. In the morning, she'll have 'hatched' her clutch, hurray! I've never tried it, but others on this forum have and reported success.

I'd have a brooder box all ready to go anyway, just in case she isn't fooled and tries to run away from the chicks--some hens will panic and try to get away, assuming that they have stumbled upon another hen's babies and are about to get their butts kicked. :)

Velvet ~:>