A dark and twisty PSL for this demon? I'm not opposed to a little fluff as well, though. Maybe demon/demon, angel/demon, fallen angel/demon, hunter/demon. It could also be interesting for a human to summon her and either have control over her or to do the spell wrong and she ends up forcing them to show her around and generally do her bidding.
I'm entirely open. I would like the line to be het (I will make you icons if you use Kris Holden-Ried, Jensen Ackles, or Jared Padalecki as your PB), but I'm not opposed to femme if it's interesting enough.