Meh, I guess I found out the answer that I was looking for (did test myself, got too impatient. LoL). There is a bug still in the 1.69 critical rebuild patch for HotU with regards to the aribeth romance. You guys can get the fix at nwnvault. And when it comes to the Aribeth romance, she is like the opposite of Deekin. For the good Aribeth, you have to persuade her and say that you love her. For the evil one, you have to intimidate her, telling that you are far more evil than Meph (persuading her and telling that you love her will always end up in a failure, as she have already said in the mimic room, you may not have my love, but my lust is all yours, make sense for the evil blackguard).
There is no option like that of Valen and Nathyrra wherein you just have to say you love them. For Aribeth, you have to have your social skills set up (which makes perfect sense since you've only known her for a short amount of time).
I like the evil aribeth ending better than that of the good paladin. Especially the moment of your death. Kinda like your sweetheart at crimes (bonnie and clyde).
Anyway, that's that. Got all the possible romance ending for the official campaigns. Started with valen and ended with aribeth. Time to retire to this game again I guess, or maybe play daggerford for one last time. =P