Broody hen -- good timing for a hatch?

Penguin has decided to hunker down in the nest box and hatch some eggs. She puffs up and growls when we open the door or even come close. Last year we had a different hen "go broody", but it was too close to our summer holiday and it would have been bad timing to try to hatch chicks. This time we're thinking of getting her some eggs to hatch! (We don't have a rooster around, so our hens' eggs are not fertile. )