@mommunism Troublesome definition: causing trouble, annoyance, or difficulty. Two out of three. What does it have to do with choosing marriage partner - that I do not know and did not asked. To not move forward after certain tragic event (i.e. the death of his wife) is, in fact "clinging to the past". And there comes definition of love. Wich may vare depending on perspective. We have no confirmation it's fairytale-like "true love" concept in this manga where two people destined to be together no matter the circumstances. What you miss her is the mundane environment (aside from reincarnation memories thingie) where circumstances with high probability may screw people and mix things up. The daugher thought of the simplest way is to move forward as still dear to each other but now separate people. I have no Idea how she intends to deal with her pretty naive dad (and here comes context for "troublesome personaly" mentioned before) so that he would move forward with his life too, but it's exactly like I worded it: "I have no idea". We don't see whole picture, we have no means to predict her path in the future so we have no real foundation behind calling her "shitty daughter".
Also, you say "just because you have new body", but mother was naturally born as completely new person now. She can live her new life, she can find new love, she can still care for her past family, but she did died, so it's supposed to be exactly the past if it wasn't for incidental miracle. And from here people involved decide for themselves hod do they treat that miracle.
P.S. What's a "SO"?