Welll... she was being scouted by hell for prospective recrutment in:
R-AA 'Ranma, the Naive Succubus' by Multiple - [Notice=Graphic Material] - [Dld Date=08/13/2006] - [Dld Size=388kb] - [Dld Files=31] - [Status=Inactive]
- [Direct] Link withheld due to content
Note that in the above, while the mainline thread is inactive, the offshoot threads are still being updated occasionally.
Hell holds her soul due to a breach of contract in:
R-OMG 'Hell is a Martial Artist' by Ozzallos-TeflonBooger - [Dld Date=08/13/2009] - [Dld Size=390kb] - [Dld Files=8] - [Status=Not Complete]
She indirectly works for a Demonic Ranma and Kodachi in:
R-AA 'The New Demon' by Multiple - [Dld Date=06/28/2007] - [Dld Size=479kb] - [Dld Files=51] - [Status=Inactive]
She became an agent of Tokimi in I think it was:
R-TM 'Child of the Goddess' by Gekigengar3 - [Dld Date=08/11/2002] - [Dld Size=456kb] - [Dld Files=10] - [Status=Inactive]
She became an agent for Elistre (a sort of dark goddess) in:
R-MULTI 'The Wild Stallion and the Drow' by Scooter - [Dld Date=03/24/2008] - [Dld Size=245kb] - [Dld Files=16] - [Status=Inactive]
There was one where Ranma came to collect her for Hell... years after post series. Cannot remember the name of it offhand though.
EDIT: Forgot one, though the last chapter has a lemon scene in it. Nabiki becomes a concubine and gets a salary and duties to a demonic Ranma in:
RANMA 'Bound to Stay' by Kalissa - [Notice=Graphic Material] - [Dld Date=05/15/2005] - [Dld Size=142kb] - [Dld Files=9] - [Status=Inactive]
- [Direct] Link withheld due to content