A far-out Cylon!Cally scenario

One of the great puzzles of BSG is trying to figure out who is a Cylon. Some characters are obvious candidates, while others seem like they would be totally useless as Cylons. One of these latter characters is Cally. Seriously - why would it even matter if she turned out not to be human? What has she done that would further the Secret Cylon Agenda in the slightest?

On the other hand, why should it be obvious? I decided that instead of being a liability, Cally's apparent uselessness could instead be a Cunning Plan. Besides, it's a great challenge. Can I think of a reason for Cally to be a Cylon that would actually make sense? Here's my attempt.

It's in two parts, for and against: First, why Cally is human. Second, why Cally is a Cylon.

( Why Cally Is Human )

( Why Cally Is A Cylon )

...you know, I almost convinced myself there. I'll definitely get suspicious if Cally ever offers to babysit Hera.