Maybe she meant well? I mean, it was also super weird for the siblings to actively choose to stay in poverty together when given an easy out... kind of makes it fairly clear that there are some toxic codependence issues going on here. It makes sense, honestly, that two siblings were abandoned by their parents at a young age and had to cope with a ton of shit.
The author's decision to put that choice on a pedestal is... perplexing. Like, are we supposed to cheer that they have opted to perpetuate their own poverty and isolation?
Their old man is a deadbeat dad who could have done anything for the past years he was gone to lift his kids out of poverty. What he did however involves going no contact with any of them and did not even pay any support for them that could help them out of their situation.
They starved during that time, lived in a dingy house, had to drop out of school, and later, took up dungeoneering just to live. They probably hoped that he'd take them in after their mother died but "Father of the Year" didn't even have the decency to show up at all to even see his kids at the funeral services. He might as well have pretended that he did not have any kids.
These two are at the point where they want nothing to do with the deadbeat bastard of a dad and would rather live poor and on their own over being taken in by a complete stranger who happens to be their sperm donor. It's a matter of principle and fucking spite at this point. They had only themselves to rely on since at a young age, no one came to help them out in their situation to a point where they don't have to drop out of school.
At this point, the deadbeat dad really do not have any rights to be in his kids' lives after abandoning them. If he wanted to help, he could have just left the two alone.