I'm currently reading 'The Haunting of Hill House' by Shirley Jackson (and enjoying it very much). However, I am confused by a certain passage. Could anyone who has read the book explain it to me?

It's near the end...

"Are you two talking about me"?she [Eleanor] asked over her shoulder.

After a minute Luke answered politely, "A struggle between good and evil for the soul of Nell. I suppose I will have to be God, however."

"But of course she cannot trust either of us,"Theodora said, amused.

"Not me, certainly," Luke said.

"Besides, Nell,"Theodora said, "we were not talking about you at all. As though I were the games mistress," she said, half angry, to Luke.

Luke is just saying that Nell is really deep in thought and probably struggling over something, right? And then Theodora and Luke have a few witty exchanges. I just really don't understand the part about the games mistress.

Thanks in advance.

She is saying that she is not the one who is setting the "rules" of the game -