Part of that is because blah blah blah spoilers, but in canon Rika's shown to have written off countless worlds because of failed attempts. There's a darker side that's hard to go into without spoiling the sequel games, but she does have a part of her that can be rather cruel. Even in the anime she's been shown to inbibe things that make someone close to her suffer, and most of the game club's games tend to have some aspect of humiliation to them. In short she's as cruel as a child can be, but taken to it's logical end considering her... um, unique situation.