Hey guys,
the reason Dm forgave Birwa regarding her mistake because he blames himself for her mistakes....b/c of him being absent for the last 10 years he was never there to teach from right to wrong or give a father's love to his daughter....so in order to proper justice he is blaming himself and realizes by being mad at her will only make the situation worse and by forgiving and showering love on her might help her change ways,,,,which is kinda helping cause so far she hasn't really caused any big problems
hope this helps :)