User blog comment:Zathronas/Analysis by an author: Dust secrets/@comment-78.42.186.25-20140823025640/@comment-24218038-20140823030027

Well we know that Penny has a semblance, it was confirmed in afterbuzz that Penny is a cyborg so she has human parts somewhere.

If there is a relation between Dust, Semblance and Aura then maybe you need all three to use any one of them. She has a semblance so she can use Dust. She most probably have an Aura too.