I follow this thread closely, but tend not to post. WBG's questions, though, really got me thinking and compelled me to weigh in because I feel like a bit of a kindred spirit with Morgan. For starters, I was stalked at age 19 -- in my case, it was a cop. I was also bullied by "mean girls" in high school.
(WBG, I'm rearranging your questions respectfully.)
My mother frequently had me tested like this as a kid. I was reading the newspaper cover to cover at age 2. In second grade I had an 8th-grade reading level. I have memories of an educational psychologist coming to our house. This was in the early- to mid-1970's, so I'm confident the testing process is much different now.
I was an active freelance music writer for several years, but have countless novels, screenplays, and short stories on my computer and in file folders that I have no desire to submit anywhere. I'm proud of them.
No one in my family knows me well. I tell them nothing of any consequence. While many people know me, only one or two friends KNOW me.
I live in my head a lot, and it sounds like Morgan did, too. Safer there.
All of the personal tidbits I've shared here bring me to this specific question ... I can't help but wonder if Morgan was a victim of child sexual abuse by a family friend, teacher, pastor, or other person trusted by the family. From what little I know of her -- and acknowledging right upfront that everything I do know is from her mom -- in my opinion, the signs are there.