Well, I am kind of not convinced, why "an ordinary teen" was sent to live with her grandparents, and then was sent to foster care ?[/QUO
A single mom in a city with limited resources, two much younger daughters? I could absolutely see sending your older child to go to high school in a small town where her grandparents lived.
My guess would be by the time she landed in Placerville, or shortly after, she probably had behaviors or attitudes that her grandparents did not allow in their household. if Julie was born in 1962, her grandparents were probably not from a permissive generation.
When I say "ordinary teen/party phase", I'm including things like cigarettes (I've read she smoked, unknown if true), underage drinking, maybe some pot, that sort of thing, BUT still goes to school, works a part time job, has friends, etc.
I'm not saying I condone those things. I'm just making the observation that I got the sense from sleuthing that she was hanging out with fairly "typical" teenagers at the time, rather than being waaaaay out there with really unsavory people, or doing anything craxy, at least not openly.