>>49650500
To be fair, we don't really know how her power works yet. I'm pretty sure it's not passive as Akyuu suggested, since Remilia makes such a big deal about "choosing" to create her own future. I think she can wish for certain events to happen the way she wants, which makes it seem like she can see the future, like a meteorite falling. But she also seems capable of knowing which "choices" are bad for her, so it's still like seeing the future.
It's just fucking weird, I blame ZUN's alcoholism.
Apparently she can also affect the luck or misfortune of others, kind of like Shion.