Monika's actions explained?

When Monika amplified Yuri's obsession, why only after Yuri died had she deleted Natsuki is really a mystery to me haha, I mean she suddenly not wanting to amplify whatever problems Natuski has, but rather instantly delete her unlike Sayori or Yuri. in this point it seems as she doesn't care or something for Natsuki or something? I really trying to understand Monika's actions and why she chose to do what she chose but...ah it's hard.

Also someone told me she tried escaping the game, is it true? I just deleted her because there was no other thing to do except talking with her for eternity haha...Please explain.

Also, were the characters programed to die regardless of the actions of monika?

Thanks a lot for anyone helping me :)