Do you see any significance in the nun who turns up in Kinbote's commentary to line 894 ("the widely circulated stuff about the nun") or any relationship between this nun and the roommate who has become one?
I think that Nabokov's intention in both the reference to a future nun "roommate" (whose I don't know, but you know my thoughts on this word choice) sitting with Hazel, and the second reference, in the commentary, to a fake nun, are both separate statements of about a certain tupe of marginal person -- non-sexual persons.