Ultimately, she's just a girl who's seen things she shouldn't have seen and has Gone Mad from the Revelation. She gets horrified when the player decides to delete her, even revealing that she didn't delete the others entirely and puts them back for you.
While she's later revealed to be a meta-aware yandere who will Mind Rape and delete her friends if it means getting closer to the player, she keeps her polite appearance even after she's the only girl left. The worst you can say about her is that she occasionally has trouble wrangling her clubmates when they argue. 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.
That said, she does use a Japanese-style spelling instead of the English standard (Monika instead of Monica).
