What did Melinda in the book Speak do that everyone in the school hates her?

Answer 1

Melinda was raped at a house party when she was in 8th grade. She called the cops and didn't speak, so the police came to the location of the phone call, in turn busting the party full of underage drinking. No one knew about the rape, so they assumed Melinda was either trying to rat them out or that she was just stupid, and they hated her for getting almost everyone into trouble and ruining the party. Also, one boy was fired from his job for getting arrested at the party.
she called the cops when she was in a party

Answer 2

Melinda called the police to a party over the summer, causing multiple students to be arrested for underage drinking. This action led to her classmates ostracizing her and labeling her as a snitch.