Someone in another thread mentioned the idea of post-partum depression. That’s not a bad idea. Her fears of their future, the taunts from the neighbours, being isolated in the village and alone…. Gives her time to mull over things incessantly and become bitter. That could explain her 180 in personality.
That would have been me…Still, in 4 years(rough estimate looking at Bae) she should have gotten over that. And at best it is grasping at straws for the plot hole the writers left. I mean it is not a logical fitting reason in the story itself.