In 1909, Cottie Sanders met mountain climber George Mallory in Zermatt, Switzerland. The two became close friends and mountain climbing partners. Cottie shared Mallory's mystical love of the mountains. The relationship between the two is elusive. She was a climbing friend or a casual sweetheart. She called him the first friend she had made on her own. When Mallory died on Mount Everest in 1924, Cottie wrote a memoir of him. Her memoir was never published, but it provided much of the material used by later biographers such as David Pye and David Robertson and a novel Everest Dream.