Wait a minute. /a/ I think I'm on to something. The depiction of Nina in Code Geass is anti-semetic. Think about it, she is a walking racial caricature, and one Goebbels would have been proud of. Curly dark hair, big thick glasses, weak, sniveling, cowardly, hateful, scheming, domineering, cruel. Jeez, you would think she walked out of a Nazi propaganda film.
However, I sincerely doubt this was intentional on the part of the writing staff. The Japs are simply so naive about how other cultures think that, to them, a gaijin is a gaijin. They have no idea how offensive this can seem in the west.