Its hard to tell precisely how my mother knew. She wrote that I was easily attracted, and always followed through on my instincts. She noted that I tended to collect relationships especially before I was married and exhausted myself in trying to please and emotionally support all of them.
She stopped the journals in late 2001 and left them to me in her will. Please note that I have 4 sisters, and the journals have divided us to a certain extent. They assume she left them to me as first born. The truth, in her words, and as I've explained to them, was that she left to me as her last act for not being able to forgive herself for my mild Cerebral Palsy. At her request, I've never shared the journals with my four sisters.
I found a great deal of pain and darkness in some of her work. I don't think they need that imagery beyond coming to grips with Mom's Alcoholism.