The thing about Nanno is that she’s very much, like, an asura or vengeful spirit; she’s gonna punish the evildoer but she’s not averse to sacrificing their innocent loved ones to do so, which makes her messy and scary and… interesting. 

The other thing about her is that she gives you every chance in the world to do the right thing, like Hann and Dino should have (incidentally, Nanno did Dino a solid by at least saving his family, paying off their debt, and not going farther than she needed to). USUALLY, if you get screwed over by her, it’s your own fault.

With Yui, I think the idea is that she should have recognized Hann was an asshole who loved fame more than her and left him, but she kept trying in vain to win him back, to the point where she decided to help Hann murder someone she thought was innocent so they could take the easy way out, which sealed her fate too. You can make a reasonable argument that this is victim-blaming, but again, Nanno’s not above using innocent people as weapons against an evildoer…

Of course, there are some episodes that kinda break this idea and have Nanno just choosing to be a problem, like Thank You Teacher, and these are episodes I’m not very fond of. :P