She's barefoot so hoof-wise she'll be fine.
I think I'll leave her out and see how she handles it, then if she's acting all weird and worried in the morning, I'll know for the next time it snows. :)
Another thought I had: the vet, when she came out last weekend, told me that Lacey has some changes to her inner eye that make it very difficult for her to see much at dawn and dusk... Would that have any effect on her safety, you think? She's a smart girl so I'm sure she won't do anything dumb but I want to check. :)