So I've got dead thrall and I really hate lydia. My question is can I sacrifice her then thrall her so she and have rest in the afterlife????

I don't think you can sacrifice Lydia. You might be able too, I haven't found anything on it. And there's a glitch with reviving the sacrifice which makes them permanently possessed by Boethia.

You are free to sacrifice anyone that you can command and who is not an essential actor.

Exactly. At least once I sacrificed Lydia and that even didn't count as an assault/murder in the stats page.

Yes this would be very nice. Possessed and undead for all eternity. Bet u wish u we bearing my burdens now don't u [censored]!!!