Quote 19
[Andy] twirls my ponytail in his fingers. […] I mumble something idiotic and run for the bathroom. I heave lunch into the toilet, then wash my face with the ice water that comes out of the Hot faucet. (44.23)
Like winks and smiles, touching somebody else's hair can be a form of violence, or at least an invasion of some people's personal boundaries. A rapist touching his victim's hair is definitely violence. Notice the very physical reaction Melinda has to this attack.
Quote 20
When Mr. Neck isn't looking, Andy blows in my ear. (56.11)
Quote 21
I want to kill him. (56.12)
Andy seems to consider being a violent predator a full-time job. Melinda is starting to feel more than fear and disgust of Andy. She's starting to feel like returning his violence.