I'm more suprised that people are shocked that black hair is the bottom. It's not necessarily that she's a beta, it's that she WANTS to be the bottom, it's her kink. I mean the whole reason she goes along with pink hairs orders in the beginning was because she originally thought pink hair was a bad person that would order her to do degrading stuff, she WANTED to be degraded. She's just a hardcore M and knows it.