My lady only has 4-day old chicks. By the time i slip them under my broody tonight and they wake up in the morning, they will be 5 days old. Is this too old???Maybe you can buy her 2-3 chicks to raise (very young, 5 days or younger). Just slip them under her at night.
From what I have read the eggs can tolerate on/off warmth initially, the tiny embryos just pause development when the heat disappears. Later on it becomes a deadly problem.