They did everything wrong. But this movie is more about why they did what they did than how it is all wrong.
The movie does get kind of misleading on various notes. Western culture, cheating is definitely a minus.
But they did do well on making the only point they were trying to: You don't just commit physically in a relationship but also mentally. You commit to understand the other person's emotions, feelings and insecurities. *But what this movie failed at is you are also supposed to guide your partner in rising above them, in healing, in creating a better mindset and not just staying stuck with your insecurities with a Mirage of a better life.
This movie is about escaping from your insecurities which lets you stay with them forever. She is actually stuck with her trauma: living in the memory of her mother's death.
It is the story of pathetic lives. But that doesn't mean it isn't watchable. You can't run away from life, and this is related to real life stories of misery and unattended minds.
His father wanted to protect her love for her mother. But he had to tell her the truth and still survive the love in her heart. The trauma might not have been a trauma.
But it's life, things happen the way they do, we choose what we choose and stories get woven like this.
The stories may be unacceptable but they can't be abandoned. Even the worst cases teach you a lot.
What we actually needed was a clear message at the end conveying the right in the wrong and the wrong in the right.