She stays crated 24/7 until broken, period.
Keep her in the cage around the clock for about 2 days. At that time, if she's shows fewer signs of broodiness (puffing up, flattening down and growling, tik tik tik noise) you can let her out to test her. If she runs back to the nest at any point (usually they don't do it immediately, but maybe after 15 minutes, maybe an hour) then she's not yet sufficiently broken and needs to go back to the cage for another 24 hours. Then let her out and test her again. Repeat until she's no longer going to the nest box.
IF the isolation cage is not safe for overnight stay (i.e. sits outside the run) then put her on the roost at night, and retrieve her from the nest box the next morning and put her back in the cage. It may take a little longer this way but better than letting a predator get to her.