Snow storm/cold snap starting today (image with temps below, will be in the teens by morning and sub-zero coming days).
Will she be ok? Should I bring her in?
I live in northern Minnesota, and our nights get down to -35F this time of year. I don't have any heat in my coop. But, my chickens are all winter hardy breeds and I have 7 chickens to huddle next to each other to keep warm while roosting. That makes a difference. Also, I have never had a silkie, and I suspect by your post that they cannot handle the cold as well as my full grown hens.
Given your circumstances, I'd bring her in until the cold snap or storm passes.
Update- silkie flew/escaped her coop
I use a plastic dog crate carrier to temporarily house any sick chicken if I have to bring the bird into the house. They are confined to the carrier, but I can put the bird in whatever room I want because I don't have to worry about them getting out and pooing on the furniture. I don't think it would hurt the bird to be confined for a few days.
How can you not bring her in? She's by herself, has no one to snuggle with to try and preserve body heat, much less manage any stress, the weather is clearly life threatening, and it appears you do not trust your heating situation in the coop...
Like I said, it gets down to -35F where I live on nights this time of year. My chickens will fluff up their down feathers to trap hot air against their body. Chickens have a normal body temperature around 105F. They can keep themselves warm in very cold weather. You don't want to have any draft coming up from underneath the roosting chickens, because that could affect their ability to trap the warm air against their bodies.
My chickens will roost, body to body, so I suspect they help each other conserve their body heat. Since you only have one chicken, she might be at a disadvantage in that respect. Again, my chickens are full sized winter hardy breeds, not a small silkie all by herself.
My suggestion is to get a dog carrier for now, and the future when you have more birds, because you can put a chicken in the carrier and put the bird in whatever room in the house you want. Since you mentioned concern over a young dog in your house, you could surely find a room and close the door to keep the dog out. I think a day or two inside the house would not be a bother for anybody.
If it's an emergency, maybe a large cardboard box would be OK for a day or two. Just cut some holes for ventilation and daylight. Chickens can't see in the dark and therefore will not drink or eat in the dark. Hope things work out for OP.