13 Reasons Why really shakes things up during season two, which is in large part due to Hannah Baker's court case. While many characters tell their truth about what really happened on the tapes, we also learn a few things about Hannah's past as one of her former classmates, Sarah (played by Makenzie Vega), takes the stand during episode 10, "Smile, B*tches."
Through her testimonial, we learn that Hannah was actually a bully at her last school. Aside from calling Sarah vulgar names, Hannah, along with two other girls, also cyberbullied their classmate by creating a Facebook page where people could post mean memes about her. It eventually got so bad that Hannah and the rest of the girls were suspended, and the girl ended up dropping out of school.
As Sarah tells her story, it's clear that Mrs. Baker is incredibly uncomfortable, as she knows how this will change people's perception of Hannah in the case. And she's right. Not only does Sarah's testimonial give the school a reason to point the finger at Hannah for being a bully, but it also makes Mrs. Baker's friend Jackie lose trust in the case. After Sarah testifies, Mrs. Baker returns home to find that Jackie has moved out, leaving only a note and her spare key.
While Sarah's testimonial certainly shows a whole new side of Hannah, it's also not the full story. As Tony later tells Sarah, Hannah felt awful for what she did. She was simply trying to fit in but ended up hurting Sarah in the process. Even though Tony acknowledges that Hannah's past mistakes are inexcusable, it also doesn't change the fact that she was a good friend to her classmates at Liberty High and didn't deserve the bullying that eventually led to her untimely death.