I'm sure Betty love to snack on people's brains by graphically opening their foreheads and eat it.

She got bullied a lot by students for wearing braces. But, one lunch day, she ate a radioactive chicken nugget with the human's flesh. She became a zombie and took revenge on students by feasting on their brains. The teachers went and saw the massacre happening. They saw Nick (school's #1 bully) getting his brain eaten by Betty. They confront her to leave him alone or she'll get detention. She then lunged at one of the teachers and feasting on his brain too. Then, she attacks another teacher as well and rips her chest open and pulled out a beating heart, putting it in her mouth, and swallowed it whole. And the principal heard that and also confronted her that she's expelled from school forever. She doesn't care and attacks her too and eating her brain and heart too. The army then arrest her for mass cannibalism and mass murder.

When NG villains unite, she was hired to be a heroine.

Moral of the story: Never bully everyone.