You go to the game’s directory and to the character folder, you monster. It makes perfect sense therefore why she dies no matter what you do. In Yuri’s case she either kills herself out of despair if you reject her or, because she cuts when she gets excited, stabs herself if you accept her confession. So, in a desperate bid to try and rescue the happy ending she tried to give you, she attacked Sayori. Monika recognized that you, the Player, deleted her likely for ALL the other girls, not just Sayori.
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