He could not help admiring her.

Nevertheless he resented the brutality of her assault on Rita and on his own promiscuous tendency, and this feeling vented itself in one last unfortunate remark.
"I wouldn't be so hard on mistresses if I were you, Aileen," he ventured, pleadingly.

"I should have thought your own experience would have--" He paused, for he saw on the instant that he was making a grave mistake.

This reference to her past as a mistress was crucial.

On the instant she straightened up, and her eyes filled with a great pain.
"So that's the way you talk to me, is it ?" she asked.