Without reading the chapter I already know why the dad gains so much more sympathy from me.
It all comes down to the weight of responsibility each party bears. The dad is under an extremely heavy load having lost a significant other multiplied by the uncertain future of single parenting, so it's reasonable that his knees buckle. Notice how he didn't actually do anything with the girl. The fact that anybody at all doesn't like what he's done despite the lack of any real negative consequence from his fling signifies the responsibilities that even the readers are placing upon him, at least to me.
Meanwhile the daughter, while having a decent excuse for her actions, has comparatively no responsibility. That also means she gets virtually no say (this would apply whether she is a child or not). However she is acting out when she bears very little weight (aside from the tragedy), to the point where I would generally classify it as entitlement. Regardless of if this behavior is reasonable, it is hardly acceptable. If she had contributed to the household and the Dad still did that, she would instantly gain much more sympathy from me and the Dad would also lose a lot since that would have been less off his shoulders to begin with if she was helping, or at least not being a recluse problem.
That being said, the author raised so many flags for a bad ending by now and bypassed all of them, somehow it's getting even more incredulous even though it should have hit the limit for that a long time ago.