What is your definition of a "green" rider or horse person?

It seems everyone has different views on things that seem to be universal. My friend had a couple two year old colts, and a yearling throughbred (who wasn't weaned at the time...!!??). My friend loves the horses, but has never ridden and doesn't like handling horses, although she has four. When her nine year old granddaughter comes over she lets her "train" the colts who have hardly even been halter started (unsupervised). The girl has ridden all her life, but has NO experience training (never mind the fact she is nine). I have told my friend that if she were my daughter, I would not allow her to "train" untouched two year olds because it's dangerous and she could do more harm than good. Her reasoning is that her granddaughter was not "green" and therefore it was entirely appropriate for her to be doing this. I was shocked that this was her reasoning. So my question is, what is your definition of a "green" rider or horse person?