Well, I am rather disappointed about this choice. Why?
1) The less important reason: this is just my personal opinion, but Devon Aoki is ugly as a sin. Dont bash on me now, this is just my point of view and we all have different kinds of taste. But in my eyes she looks like an incarnate manga-nightmare.
2) The more important reason: if I take a look on all the pictures that show Valerie Duval (sourcebooks, trading cards, comics, etc), than on none of them she looks asian or childlike. She always has a very european look, a longlish face (and not round like Devon), high cheek bones and a more prominent nose and chin. For me Valerie has a very graceful, noble and proud, but still feminine beauty like (the young) Claudia Cardinale or Catherine Zeta-Jones have - unfortunately Devon Aoki has none of this....
PS: Dont missunderstand me, I liked Aoki in Sin City, but I do think that she just dont match for the role of Valerie Duval.