User blog comment:Zathronas/Speculative author, Volume 3: Jaune Arc/@comment-25405817-20141120135316/@comment-3387274-20141120204252

I have oft thought that it would be a form of energy, possibly electricity. Suits her hyperactive streak very closely, as well as being erratic and destructive, not to mention spectacular. And also fits with the Thor motif quite well.

Never decided whether she could access her semblance or not. On the one hand she can clearly keep up without obviously using it, so she could be extremely overspecialised towards not using Aura (which would still contrast with Ren). On the other hand, the current presentation for semblances seems to imply everyone at Beacon learned to use them already, in which case it could be she isn't using it because it would be dangerous if let off at random.