Why does Root refer to the Machine as "She", not "He"?

This previous question about Person of Interest already asked why everyone else but Root called the Machine "she" rather than "it". But in this question I'm more concerned about why Root actually calls it a "she", rather than a "he". I am asking about Root because she started calling it "She" and others have simply followed the trend, as indicated by the answers to the previous question.

I understand that Root considers the Machine an intelligent being, even superior to humans. Later, she says she has an intimate relationship with the Machine. So, that helps me understand why she doesn't refer to it as "IT". Still why simply not refer to it as "He"?