User blog comment:Zephyrcoil/RWBY Volume 2: Commentaries and Other Information/@comment-25258408-20141128034421/@comment-4010415-20141128172743

Weiss' semblance has nothing to do with ice. Pyrrha specifically said that Weiss' semblance is her glyphs, the circle symbols that she creates!

The pillar of ice may have just been her using a glyph in combination with ice dust.