Everything being magically resolved in the last page does sort of leave a bad taste in my mouth. It seems kind of pointless to build up the tension of "oh no, I fell in love with my niece, what should I do, how does she feel about me, is there something wrong with me, is our relationship going to survive or fail and it'll be my fault" and then just completely resolve it into nothingness.
No idea where you got these ideas..
But where exactly was it said that the aunt has only realized now that she was in love with her niece, or worry about the functionality of their relationship?
To me, this short story has implied that their relationship has been like this for quite a while, it's literally said in the last page that they've been living together for five years. It's clearly just the aunt being paranoid..