I wonder if we will ever find out? This case received some media attention, but not enough to learn about the family dynamics at play. I wish some good true-crime writer would take a closer look and write about it.
IMO The family dynamics were all concealed under the umbrella "Sydney is schizophrenic and was insane at the time." Pointing to one member of the family (a kind of scapegoating) as being individually the cause (and then letting her off on the grounds of mental illness) blurs the context. IMO the impulse to kill was not in a vacuum.
If Sydney was insane, she coulda randomly killed someone else, but this wasn't random, and there was a preceding history of lies and denials.
Also, the family seems to have very black-and-white thinking. Sydney was a "good girl", a "good student", and therefore she couldn't be bad in any way. Brenda saw the lies, and this seemed to turn Sydney into something less than good, when, in reality people are complex and textured, and EVERYONE lies. Sometimes lying creates boundaries and distance, and young people need this!
IMO something seems very off in this case, because family claims to "speak for Brenda" as though they know what would be in Brenda's head, "Brenda and Sydney were best friends" (this gets complicated, since moms are supposed to have the duties of moms, not peer friends), the veritable STACK of lies and denials. I dunno, but the 24/7 tracking of the family members with 360 (or whatever that app is called) seems very intrusive and problematic to me.
Heck, I wouldn't have been wanting my parents to track my every movement when I was in college. There'd be no room for boundaries, privacy, exploration of the world.... And the parents kept relentlessly hounding Sydney about why she was in one place or another.
We know about the tracking because Brenda would ask Sydney why she was spending so much time at the library (SP lied and said she had a job there), and also because Dad left his phone at work so Sydney wouldn't find out he was headed home to check her out.
And why were the parents rushing home to check things out? I don't get this either.... They could easily have made the necessary phone calls to campus from work and connected with Sydney later. Why was it so urgent?
Why was 360 needed, rather than just occasional texts between family members?
Myself, I would HATE all this scrutiny and urgency. I'd be lying all the time. I would unlikely have been in denial mode internally (IMO this was a big part of Sydney's problem), but I'm sure as heck not giving out the secrets of my life to my parents!