OKAY BASICALLY: the Organization usually sees Xion differently. Most of the time they see her with the hood up, because she originally had a blank face. Roxas is the first one who starts to see her as Xion. HOWEVER, in ONE scene, Xigbar is actually battling with her and he sees her as Ven (and it's Ven, NOT Roxas, since it's in Ven's clothes and everything) and Xigbar is talking as if he's met Ven before.