Kiara, when given the leeway, is a straight up evil woman. Of all the breast, she happens to be the worse (so far... We'll see what the Foreign God does). She lives to tempt people into depravity, ask EMYIA Alter about how that goes. Without her warped mindset, she could honestly save people like a messiah... she ends up being that selfless. The character that you see in Chaldea is from the same universe, only to have been "enlightened" what she is truly capable of and turned into the Mother of all Thots.