Are you telling me this isn't just someone's nightmare? What a weird plot indeed, even though my initial thought was she's a cousin, before reading someone else suggest this is a dream.
It's pretty sad Lee Gigo was so drawn to her and didn't hesitate to spend private time with her, just because she looks and behaves like Oh Roji. At one point he even realised he shouldn't be doing it, but then he just continues nonetheless. If Oh Roji feel some sort of inferiority next to Oh Riji (she's supposedly copying Oh Riji's style), Lee Gigo paying so much attention to Oh Riji is the last thing Oh Roji would need to experience.