I don't think it's fake snow. There's no way to know for sure, but there's something about that one that makes me pretty sure it's a candid shot of a regular girl. Looks like she may have just got off of a bus.
Here's some "real life" school girls. Not candid, but still casual, and the girls who turn around to give the "V" get extra points for playing along nicely when they know they're being filmed.
@Haladflire65 - I've always been under the impression that Tokyo got pretty cold in the winter, but looking at a map I see it's around the same latitude as the area about halfway between San Francisco and LA. I always thought it was further north.