In the beginning, Elsa knew something was up; Yvonne's actions and attitude didn't match every time bullying happened. She knew that Yvonne couldn't tell her why for some reason... though that reason is gone now. Also, I wish we knew EXACTLY Elsa remembers. I mean does she know about the entirety of the game system like Yvonne and we do? Dorothee's information might not be precise either, so who knows... Either way, the fighting is really dumb, considering the entirety of the story.
If you start questioning everything, then you get the fun times of, "Did you stab me because you knew that'd make me love you?" and other ridiculous things that make zero sense.