User blog comment:Zathronas/Analysis by an author: Volume 2 episode 11: No brakes/@comment-3146930-20141024021616/@comment-24218038-20141025002149

The RWBY cast actually talked about that yesterday. They said that Weiss has a better variety and quality of dust than what is normally sold. Thus the increase in Blakes fighting ability.

And no, Ruby and Yang haven't tried her dust yet.