I was just about to post this exact thread, now I'm going to look like a tool.
I like the idea of the Brute and the Dark Chick working together closely a lot more than the Dark Chick also being the brute. As has been said, their roles don't really jive with each other. It would also give the villainous band a nice little 'sub-group' thing that isn't a quirky miniboss squad.
I have kind of a cool/funny mental image in my head of the Dark Chick and her werepolarbear 'animal companion'.