Maria arranged the marriage between her brother George I of Greece and her cousin-in-law Olga Constantinovna of Russia. When George visited St. Petersburg in 1867, she contrived to have George spend time with Olga. She convinced Olga's parents of her brother's suitability. In a letter, her father Christian IX of Denmark praised her for her shrewd arranging of the marriage: "Where in the world have you, little rogue, ever learned to intrigue so well, since you have worked hard on your uncle and aunt, who were previously decidedly against a match of this kind."