Estelle Cole was a woman who had known Jack Harkness during the War. When she later met Jack again in the 21st Century, she believed that he was the son of the Jack she knew.
While walking through Roundstone Woods she encountered the Fairies after spending her life looking for them. However, she saw them as good, friendly creatures, and never realized their true nature until they killed her by invoking a heavy storm above her.
She had a cat named Moses.