Who is Damiana from Memories of My Melancholy Whores and what is their importance?

The narrator's housekeeper, Damiana, is cherished by the narrator for more than her housekeeping skills. He became so enamored with her one afternoon while she was doing laundry that he forced himself upon her. Afterward, he increased her salary with the agreement that she would allow him to indulge his needs once a month. The narrator's relationship with Damiana is the longest he has ever enoyed with a woman.