Well..we never got above -2F so far today. I decided to let her out of the cage, since the coop itself is sitting at 12F. The sweeter heater warms her from above, but the cage is a wire kennel, so she is more exposed to the coop temperature around her. I think it does take the edge off for her at night. She left the cage, jumped up on the coop roost, and is now just sitting there. I'll continue to observe her, and will probably put her back in the kennel for the night. Or...just let her be and see what happens. At these temperatures, the other 7 chickens are mostly just sitting around staying warm. They occasionally saunter off to the waterer and feeder, then go back to sitting. So the sitting part I'm not too concerned about, since this is normal when it is very cold. The issue I have with her, is that she sits, and never visits the waterer or feeder for the entire day, when the others do. I give her the warm, wetted mash in the morning and evening, and she gobbles that up just fine.