When Melinda writes Andy as a guy to avoid on the bathroom wall, it becomes clustered with responses that agree with Mel and talk about how horrible Andy is. Making it better is that it comes right after Rachel refused to believe her about Andy being a rapist.
David and Ivy's genuine and unquestioning acceptance of Melinda, a social outcast and supposed 'freak'. Especially in Ivy's case, as we know she was at the party. If nothing else, it's nice to know that not all teens have to be monsters.
Melinda's somewhat distant-seeming parents buying her drawing pencils and a sketchbook for Christmas, because they notice she's drawing a lot.
In the movie, when Melinda writes the truth for Rachael, the latter expresses genuine shock and concern for her, despite that they are ex-friends. Sure it backfires when she doesn't believe who raped Melinda, but in that moment, she was pretty caring for someone who drifted apart from Melinda.
The ending of the book, where Melinda starts to really open up to other people and tell them about what happened, describing it as feeling like the last shards of ice in her throat had melted. In the book, the person she opens up to is Mr. Freeman, the only teacher who seemed genuinely concerned about her and encouraged her. In the movie? It was her mother, who was shown to be concerned for Melinda at several points in the story, especially when she woke her up from her nightmare about Andy raping her.