Origami's quest to avenge her parents ended with the revelation that SHE was the one who killed her parents. That alone would be horrifying enough, but when you take in account of how she got to that point. Her hatred towards spirits were so strong that she joined DEM in order to gain enough power to kill them upon realization that she's come to accept them, even risking her friendship with Shido (She already tried to kill his sister once and she was stopped only due to passing out from using the White Licorice) . She even decided to become a spirit just so that she could have enough power to kill them. In the end, her entire life's work ended up All for Nothing. Is it any wonder why she inversed?