I'd say they were just very good friends, (Barti and Queez) I know in the first book he mentioned that two djinn fell in love and one of them was charged to kill the other and the djinn ripped in half trying to disobay his charge, so that their relationships nowadays were temporary to avoid that sort of thing happening. Besides maybe the "girl of unusual beauty" thing was just an observation. It's as if a girl says "Wow, that other girl is pretty." (and she's straight) Anyway, it never specifies whether or not demons have to breed or even HOW if they do have to. Maybe I should ask the author.
Hah! Checked the "ask the author" section and they don't fall in love, or breed!
I didn't vote, even though there's a possibilty she's alive I think she's dead but my internet is being wierd and won't let me vote right now.

I say night I'm living in the forest of my dream,
I know the night is not as it would seem,
I must believe in something,
So I'll make myself believe it,
That this night will never go.
Laura Branigan, Self-control

Oh, Canada...