Who says, “My mother, you know, has been spending the winter in America, and we’re expecting her back. She writes that she has discovered a niece and that she has invited her to come out with her.”

From the text:

Then young Mr. Touchett explained. “My mother, you know, has been spending the winter in America, and we’re expecting her back. She writes that she has discovered a niece and that she has invited her to come out with her.”