Purple hair is a result of being reincarnated by the Demon God rather than one of the other seven gods. If she overuses her Unique Skills to point where her 'soul vessel' (not sure what that is exactly) cracks she'll turn into a Demon Lord. Kind of like damage resulting from overexertion where runner develops permanent physical damage in chest and legs from running too fast for too long without rest. As for the kingdom's ruin and her cursed titles will have to see if result of divine retribution or conspiracy from mortal enemies. Personally I feel that if had done a taboo according to the gods would have heard from oracles or voice echoing across heavens screaming taboo, also couldn't be judged and receive divine retribution since punishment for a taboo has to be a unanimous vote from the seven gods and one of them couldn't vote due to still being dead from being killed by Dragon God. More likely it was conspiracy done by enemies of the family, corrupt nobles wanting royal family to fall, and dirty tricks from enemy country that invaded and took over. Since Arisa's methods are at least decades ahead of their time, unheard of, and garnered results along with most people being uneducated, superstitious, and timid folk it wouldn't take much to sabotage her efforts, spread malicious gossip and false rumors, and other dirty tricks to scare people into being afraid of the royal family over nothing while making the invading country look better for 'stopping' the royal family's supposed heresy and squelching any possibilities of rebellion or reinstating the survivors of the royal family. After all, Mia pronounced monsters forming from compost as unfounded rumor with no basis on fact or reality. So reports of monsters coming from Arisa's compost were all lies.