[Snowfall]

As a guess, I'd say White Wizard is using the female as Rider as a replacement for Haruto. He's already expressed disapproval of how powerful he's become and ep.34 made it seem even more likely that White Wizard is Wiseman. We'll probably see her show up in the last few episodes, fight Haruto, learn what she's doing is wrong and join him and/or die

A Golden form was pretty predictable for Wizard. I doubt we'll see it beyond this movie though.