So I'm guessing Komaki fell in love with Wakaba at some point in elementary, then Wakaba fell for some guy in middle and Komaki decided to get back at her for that betrayal (self perceived), when she saw how easy it was to seduce (and get rid of probably) the guy and the emotional look on Wakaba's face she probably opened the door to the Sadism kink, Wakaba probably also stopped having matches with Komaki at some point before which would make Komaki lonely and she saw the act of betrayal as a means of spurring Wakaba to challenge her again even if in anger.
She probably wants Wakaba to remain the only person who never treats her like everyone else does, even if she has to ruin their friendship to ensure that at least the person she likes never stops treating her like a human being.