I read like 5/22 of the webnovel

https://ncode.syosetu.com/n1537gp/16/

I read a few relevant seeming chapters using shitty Google translate. Take what I say with a grain of salt. From what I can gather is that the dad doesn't talk to MC because he loved his late wife so much he's constantly reminded of her, their love, and her death when he looks at MC. He also loves MC so much that he couldn't stop thinking about how devastated he would be if she died as well. In addition, MC reminds her dad so much of her mother that he can't give her his love. He decided it would be best for him to get involved with her as little as possible

The stepmother has a complicated past. She was raised being told how cute she was constantly. This lead her to flirting with a lot of boys and having no female friends. By the time she was of age, no serious marriage proposals came her way. She easily fell in love with shitty guys who left her for richer women and was branded a whore by society. By the time MC's dad proposed to her, she was absolutely done with love. Their marriage is purely political and she promised to take of MC for her.

Stepmother does think that MC is super cute and angelic from the moment she sees her. However, she's a jaded 19 year old so her best idea to help her is using words opposite of what she was showered with growing up. Stepmother genuinely wants to protect and raise her and shower her with lots of love. She believes telling MC she isn't cute will protect her from future strife. MC overheard her stepmother confessing in her biological mother's room about all of this and reflecting on her actions so far. At the end, they had a heart to heart and reconcile. While the resentment isn't completely resolved, MC feels that her stepmother had her reason and did love her and wants to stop dwelling on the past.