My heart goes out to her. She seems like such a good person but of course the kind, empathic people are often the ones targeted by abusers.
I relate in a small way as someone who has an NPD for a brother. Narcissists often target empathic people. So I wonder if her ex is an NPD. Of course he would see her leaving him as a declaration of war if this is so.
I wish she was able to stand up to him. It is the most healthy thing she could do for her child. I have recently started writing on Medium about my experience with NPD. It's really helped me and I hope it helps others. I hope your article also helps others.