Like the reason for all the change in their actions WAS LITERALLY EXPLAINED THERE. They felt an incompatibility with the soul that resided in the body. And as per the rule of their world, and many other worlds mind u bc this isnt even the first time this was talked about in a manhwa, when the body and soul dont match, unfortunate things tend to happen and those unfortunate things tend to be those that are not within humans' control. As in, you cant blame her family for that because they were only reacting to the INCOMPATIBILITY that was enforced upon them by the world. It's a whole conundrum because you cant actually even hold them accountable since they only ever reacted to the existence of the wrong soul. This is like the FOURTH MANHWA ive read that talked about the dangers of a soul not being in the right body and its consequences to both the body, the soul, and the people/world around them.
I feel like a lot of the people in the comments arent understanding the premise of the story enough.