Is it for your theoretical daughter? Or is it for yourself?

Do you think she would like having the fairy tale name? Or do you simply think it would be neat to have a daughter with a fairy tale name?

I know she doesn't exist yet, but in the end you should consider her theoretical future perspective above any others, including your own. After all, naming a person is not the same as naming a pet or a video game character ... in those cases the thing being named doesn't care what its own name is, so you can feel cool about making a cool name for it, but a person does care, and has to be called that name, and has to carry that name everywhere they go and in everything they do.

That said, if you're set on the idea, I do suggest making Snow a middle name. I don't really have a problem with unique first names, but this is a different matter, setting up the first name to match with the last that purposefully and flashily is asking for trouble -- the seven dwarves jokes she'd get would only be the start of it. Some kids will grow up to embrace a purposeful name like that (as some grow to embrace unique names), but not every kid will, and you shouldn't name a child based on an assumption about how they are going to grow up.