Has anyone tried this? It seems like it'd work pretty well, but I don't know if it would cause any problems.
https://aonprd.com/PrestigeClassesDisplay.aspx?ItemName=Pain%20Taster
I'll be honest, it almost seems designed for Laori.
The problem I foresee with this is that Laori is very not useful to the party, except in what spell utility she can offer as a potential first if not second cleric to the party. Trading cleric levels for pain taster directly strips that for no great mechanical advantage (welcome to the age when PRC's were almost universally bad).
Plus, giving her levels in this makes it harder to justify any redemption your players may wish to attempt on her as a result of the events in Scarwall. If she's just a full ex-cleric, at least she can be guided to or find another god, but if she has this entire other class taking up half of her levels that she refuses to further engage in, well... it requires even more hand-wavium to make sense.