that is not needed for the little kid to know what happened in the past...she is a kidshe wanted to know why her father left her...she got the answer he did not know her existence and that gives a closure to her trauma...
LOL
So you're saying that knowing her mom lied to her dad gives her closure even though she doesn't know why she lied? That's not closure that's incomplete information.
Also your argument is so self-contradictory cause you said she's a little kid so she doesn't need to know everything. So why not just leave it at "your dad didn't want you or your mother cause he was in love with another woman for now. That's enough for a little kid. Plus Mishti had heard the conversation both between Kunal and Mumma and the argument between Kunal and Mishti, so I'm sure she knows that Kunal didn't know she was his daughter until recently.