Mystery Murder Book

I remember reading this mystery murder from a teacher's small, shabby, library back in like 2010. It followed a teenage girl who didn't agree with the rest of the town that her best friend (and eventually she realizes also her crush), committed suicide. The town essentially comes too a conclusion that he listened to emo music and therefore his music made him want to die, but she insists that she knew him well enough to know it just couldn't be possible. It bounces between her internal conflicts about possibly being wrong and her love for him, with flashbacks, and her insistence on finding out who framed it as a suicide when everyone else in town thinks she is delusional and just want to cancel emo music. She finds a female officer who at first refuses to help, but she drags them into helping look for clues and just as the officer is about to give up, the girl returns home to a man trying to kill her and remembers how there was some kids they never let into their treehouse when they were younger and one of them had a brother in that ended up going to jail. Eventually that brother had come for them.

I could be wrong about the next details, but I believe the boy that was murdered was named Emmett and the guy that went to jail was actually framed by Emmett and the girl when they were too young to know what they were doing. Also I believe it was mentioned a lot that they lived right next door to each other so she was used to him just climbing from his window over to hers all the time and that was also why they kept the treehouse as just for them. Also I think I remember the book back or front cover saying "Suicide... or murder...!?" or it was "Murder...or suicide?!" But on a website where you can search books by the cover words, I never found it.

Secret, Silent Screams by Joan Lowery Nixon?