The usual convention is that the personality overriding the villainess is kind and harmless so the "original canon" where the villainess bullies the heroine and gets exposed has no reason to happen, in this case the overriding personality would be far worse and more obnoxious, making the proverbial trip to the gallows that much faster.
@dummycake That's why I specified stereotypical. The fedora-wearing, katana-wielding, asocial NEET kind that feel the need to be correct all the time. Think Slappable Jerk, if you've ever watched him.