Mere mind main kuch aaya hai..
So Walnut-Monami should have a showdown and Monami should say in anger that maine sach bol diya toh u wont be able to tolerate it..
Truth being that Monami's mom suffered from ptsd at that time but she couldnt speak about it and she knew her husband wont understand..she didnt want to leave her daughter but it became too much for her..She writes a letter to Monami saying that she is sorry that she wont be with her anymore but she will always look after her from above..(Monami could be 7-8yrs old at that time)
When her father comes to know about his wife's death,he refuses to believe it was due to PTSD because he sees it as a weakness and he blames the Army & Army people for her death..(refuse to accept that he could have helped/supported her)
Monami ko baad main pata chalta hai(few yrs down the line) maybe unintentionally from her mother's friend..she thinks ki agar uske father ne required help or support di hoti toh her mom would be alive but she doesnt make an issue out of it kyunki she is that suppressed Monami
That's why she even understands ki what Karan went through..
Finally she reaches a breaking-point when her father tries to break relationship with Karan amd she lashes out saying that he never understood what love,mutual understanding & support is..
all he thought about was his money,legacy & reputation uske aage kuch bhi nahi..
She always wanted his love & acceptance but finally realised ki jo unke paas hai hi nahi woh cheez usse kaise dege..