Request #215

Hello! I’m trying to remember a book I read when I was 11 in 6th grade. I’m 31 now, so the book was definitely not a recent book. It was about a teenage boy trying to uncover what he believes is the murder of his girlfriend. She was believed to have committed suicide from carbon monoxide from her car in the garage. (Spoilers) I know the ending involved him uncovering that it was really the girls mother who somehow had forced her into the car, I believe? I think her mother was somehow jealous of the girl or wanted the attention from the public that her daughters death would bring? It wasn’t a large book, and the chapters were rather short. I believe some of them could be just about a page or two long, so you felt like you were reading really fast. Thank you in advance for the help!