Cal could easily have worked as the female equivalent of the Gentleman Assassin - elegant, refined, well-mannered, and applies the same principles to her murders by always killing people in a manner she considers polite and not too messy.
What we have instead is a vain, bratty kid with horrible manners and a bizarre obsession with violence and gore. She doesn't come off as anything like what an assassin should be, let alone remotely "badass". Brattiness and arrogance with nothing to back it up are not badass - they're just really really irritating.