If she is huddling then she is likely cold.
My silkies are with SO many other chicken bodies in the coop that they stay warm. I only turn on light bulbs for my chickens when it is around 20-28 degrees (around here, that is usually only for a couple of weeks each year).
If I had just 3 chickens in a coop, and one was a silkie, I would run a light bulb for them when it fell below freezing. There are many differing opinions on heat in the coop here on BYC, but my silkies are really not as hardy as my other chickens I have noticed. They act cold sooner.
THEN, if the power goes out, having kept them warm with the light, I would bring them in the garage.
If you consistently run heat for chickens, they will still need it when the power fails. They might die, when they might have survived if not acclimated to the heat.
Oh, and when I run light bulbs, I only run 100 watts. For very small coops a 60 watt may be enough- I have used those. Heat lamps are really HOT. Always secure your light two ways, and don't just clamp it. The chickens will bang into the light many times and knock it down.
Light bulbs in coops are dangerous.