Caroline rejects the difference principle

Joey got to play video games while Caroline was at ice skating. So Caroline thinks that she should get an equal amount of video game time, and Joey can't be allowed to play video games during that time. He can't even watch her play, because then he would have more video game time than her. I try to reason with her. Me: "Suppose you have two options. In one, both children get one cookie. In the other, once child gets two cookies, and the other gets three. Which is the better option?" Caroline [shouting]: the one where everyone gets THE SAME. Everyone should get THE SAME. Me: But you would get more in the other option. Caroline: He has to get the same as me! You only let him get more than me because you like him better! Me: But that's not rational!