Dieties and Demigods, Kit.
I don't know if CE is the right alignment. I'm seeing her as more LE, maybe as the God-Queen of the wights. I think it's the tail; it just screams "Alien" to me.
(Alignment), Death, Evil and Undeath (FRCS) would probably be the proper domains, but Madness (D&DG) would be good if you follow up on CE and the tail spike idea, and Pain (BOVD) might also work. Her portfolio would probably be, just off the top of my head, cruelty, undeath, casual suffering and necromancy.
Ooh, perhaps she should be a consort or rival of Vecna: so many ideas...
Demiurge out.