The Mad Typist on OpenSalon bemoans the lack of female leads in Pixar films. Even better, she puts together a sharp, spot-on discussion of the major female characters in the 9 Pixar films released to date.
The only point I would disagree with is Collette from Ratatouille, and even then only slightly. Collette is a strong female character, and clearly was included as such. Early in the film, she's actually in the position of teaching the "genius" chef how to work in a professional kitchen.
The Mad Typist is correct that Collette ends up being relegated to a strange secondary role, but a big part of that is the film's narrative confusion over whether Remy or Alfredo is the primary character. It's hard to argue though, that in the end, Collette is sous chef to a rat, and seems happy in her subservient role.
So's it's a character with potential, but ultimately, the film isn't sure what to do with her. I'd give Ratatouille a B- to the Mad Typist's C.