Board Thread:Episode Discussion/@comment-4010415-20170717151617/@comment-26397825-20170718010535

SpiritedDreaming wrote: And I thought the thing with Weiss drawing the flames up the blade was a callback to Cinder doing it with the fire dust in her dress in Ruby Rose. Maybe concentrating like that makes stronger dust attacks as you condense your aura in it or something. I think I may have edited this in while you were writing your comment, so you might not have seen it.

She didn't concentrate on a blade beam/aura slash in any of the previous battles (for whatever reason), and in fact that is the first time we've seen an aura slash with dust included. We don't know the rules - for all we know the amount of aura in an aura slash simply amplifies the strength of the dust, but it's more costly than usual so that's why Weiss doesn't do it.

Or maybe it was just a visual effect they decided to do for the sake of it to show off all the cool things they can do with Maya now, and it has nothing to do with her actual power levels or anything. A bit like the Red Trailer is technically canon but it's more of a trailer for Crescent Rose than Ruby herself.