This is the title of her autobiography.
As she says:
What are you saying? Who am I?
Well I’m me — I’m what is called the power behind the throne. I’m your — your character. Isn’t that what they call it?
Yes, Kate. That’s what we call it. Character. You were certainly an interesting Character.
Character: a configuration of habits.
Oh, but Kate, we have another word that you never knew much about. The word is Temperament.
What you didn’t know was your Temperament. But I doubt if you would care. You had an interesting and full life anyway. However, you might have understood yourself and others a little more.