Even if 15-year-old Melinda weren't socially quarantined, it still wouldn't matter. She's not saying much at the moment. All words have evidently been buried beneath an endless torrent of pain, despair and inner anguish at the precise time--start of 9th grade--when speech of some sort would seem relevant. Between her parents vicious bickering and the determination of her once-close-friends to ice her out, there's not only nothing to say, there's no one to say it to. Isolation seems to be her only companion ("a reliable anesthetic") as the days, then weeks and months whither away.
Anderson won the Printz Award for this stark depiction of one girl's emotional paralysis amid the suspended shock of an undisclosed trauma. Without knowing the plot synopsis, readers may initially misinterpret the reality of the situation; especially as the focus exclusively tracks Melinda's conscious at present, omitting all but the bare essentials. It's pretty late in the game that particulars resurrect themselves, ultimately exposing a justifiable reason for the silence.