Speak 1-100

In the first 100 pages of Speak it is her first day of school. She is so nervous because of the last party she went to when she called the cops, but why did she call the cops? On the first day she meets a new student. Her name is Heather. She is really into trying to be popular and so she has Melinda try and help her. Little does she know that Heather is just using her. She will later ditch her for the perfect girls who help out with everything all because she called the cops. Why?