How is what Harriet wrote in her notebook the truth?
To me they seemed more like her observations. How are notes like "Janie really creeps me out..." a truth? That's obviously an opinion. As much as I love this movie, Harriet just obviously couldn't take what she dished herself. When she peeked at the note that regarded that she stinks, she felt just as bad as her classmates when she made fun of them.
I'm so surprised at how many people are rationalizing Harriet's action in order to make her seem like a cool protagonist, when it was obvious that all of these kids had their flaws. Was Marion awful? Absolutely. Was Harriet awful aswell? Yes.