She was supposedly burning with hatred toward you but decided to hide that for about 1 fake year and kept it to herself after the initial scene, pretended nothing was wrong and not being vocal about it, not confronting Sensei at all to suddenly drop it like a bomb on everyone, even lying beforehand pretending it was gonna be a normal gag she practiced for.
She wasn't the "bad guy" but she certainly wasn't the good one either.
I think you're missing the point of why she chose to bring it up disguised as a joke.
Unfortunately, the Predator is surrounded by zealots who live in denial. Everyone knows something happened between him and Molly, but only Kirin apparently put things together or cared enough to do so (besides likely Maya).
Tsuneyo's comedy routine was a scream for help that no one even considered taking seriously, which is fortunate for Tsuneyo as she'd become an enemy instead of a weirdo for "slandering" Sensei. It was however a reminder to Sensei that she hasn't just forgotten what he's done.
Tsuneyo also wasn't exactly angry. She was more confused by how he still continued to deny it (remember she was the first to confront him), and how Molly has just decided to move past it. It wasn't until they reconciled that Tsuneyo did this. It served mostly as a warning to everyone. Including us.
Tsuneyo is far smarter than she lets on, and she doesn't exactly have much to lose.