In my headcannon, Mysterio does this to Twylight after using her. And when she calls him a gaslighter, Mysterio points out her hypocrisy; the Marer Do Well and Walking Dead hoaxes,the division between Rainbow and Rarity involving the swamp,the cheerleading gambit, her doubts in Pinkie which nearly got many eaten by a hydra and some parasprites, her betrayal of her own niece, her Lesson Zero, how she try to rob Novo, how she prejudice Tricks and Dyscord as well as Capper, and her abuse of the CMC for Cozy Glow. Comparing her to himself and showing images of harm. And using illusions of many criticising and chastising her until MJ and Spider-Man reveal its all trickery to mess with her, and defend his her errors Zero justifies Mysterio’s sadistic gaslighting.

I remember when Mysterio need with Peter. Jerk.