Despite one of my older theories, I no longer believe that Spencer is the one to have “killed” Ali in a fugue state. But I do think her parents believe that she may have. All the shady stuff with the Hastings would make sense if they thought they needed to cover things up. Hiring the PI, burning the field hockey stick, not believing her accusations against Ian, her mom defending Garret, Melissas insistence that she’s been protecting Spencer, etc. It all ties together if they think she accidentally murdered Ali. It’s possible one of the Hastings saw Spencer awake and incoherent that night.