I'll let you guys refer to the top of this thread if you run games using the Itch desktop app, but here's how you open the game files if you need to delete Monika or need to look for some files in the game's directory (no Itch desktop app).
It's the same folder you opened DDLC with, unless you're blind or something. All the game and character files are there alongside the Application for Doki Doki Literature Club, plus some. Hope that helped.