My humble opinion is based on my psychology major and studying abnormal psychology. While I'm no expert on this subject (although I hope someday to be able to say that I am : ) the topic of nature vs. nuture comes up when you are comparing notes on how people react to bad situations, including be abandoned by a parent.
My point is simply that no matter what the author is projecting, and I'm sure she has a point, I was trained to challenge the idea that "nurture" or environment has more to do with a person's ability to cope or outcome in life than "nature" -a perspn's biological predisposition to be able to handle trauma.
In other words, your life has less to do with what has happened to you, and more to do with your interpretation and reaction to what has happened to you. Does that make sense? I find this interesting...