In later life a bull fight was to appear to her a tiresome affair, but the domination of one human being over another, absorbing.

She had, too, at the very earliest age, that conviction that it was pleasant to combat all sentiment, all appeals to be "good," all soft emotions of pity, anything that could suggest that Right was of more power than Might.
It was as though she said, "You may think that even now you will get me.
I tell you I'm a rebel from the beginning; you'll never catch me showing affection or sympathy.

If you do you may do your worst." Beyond all things, her anxiety was that, suddenly, in spite of herself, she would do something "soft," some weak kindness.

Her power over Mary Kitson reassured her.
The fascination of this power very soon became to her an overwhelming interest.

Playing with Mary Kitson's mind was as absorbing to Sarah, as chess to an older enthusiast; her discoveries promised her a life full of entertainment, if, with her fellow-mortals, she was able, so easily, "to do things," what a time she would always have.