Alas, Poor Villain: When the player deletes her file in Act 3, her first reaction is to act horrified, then angrily berate the player for doing so when she realizes what's happening.She's just a girl who's seen things she shouldn't have seen and has Gone Mad from the Revelation. She even offers you some genuinely good advice from time to time and sincerely opens up to you, as any good girlfriend would. She really is that friendly, and she really, truly means it when she says that she loves you and that she wants to make you happy. Affably Evil: Uniquely for a Yandere, nothing about Monika's apparent kindness and politeness is an act.
That said, she does use a Japanese-style spelling instead of the English standard (Monika instead of Monica).