Now that we've got that cleared up, let's talk about the significance. In the tv show, Keiko at first seems to serve Nanami out of loyalty. But, in episode 21, we learn that this is not the case (see "Spotlight").
At this point, we also learn that Keiko feels as though she is a low class person, an inferior being, compared to Nanami and Touga. In fact, that could explain her physical appearance, why she is portrayed as she is. Keiko, Aiko and Yuuko all together are represented as the "normal" girls, the commoners, because of their hair color, it being brown. Brown hair is often considered as a commoner's hair color (ack! then I'M a commoner! ^_^;;).
Phew...now you know why this shrine is named "Inférieure" ^_^