User blog comment:Tatmtn/Character Appreciation: Ruby/@comment-25405817-20141222160709/@comment-25555436-20141222161921

Or...Alternate Character Interpretation:

Penny is a "person", in sort of speak, but she's technically a weapon designed to exterminate Grimm and use Aura to do that. Developing a personality is secondary.

And, we all know Ruby loves weapons.

I believe you already get my point.