I used to think that maybe the final 5 weren't evil, that they would somehow help the humans...but not anymore. After Tory killed Cally, it's pretty clear she is evil, or at least, she's not a savior or anything. I guess she's actually human in that she was only concerned about her own life.
Well, to some degree I think you are right. However, the cylons (and the humans for that matter) have made a huge deal out of Hera Agathon being a human-cylon hybrid. We now know that Nicolas Tyrol is also a hybrid. I suspect to some degree at least, Tory's actions were designed to protect Nicolas and perhaps even ensure that he remains under cylon control/protection.