Eugenia McDonald was born around 1845 in Washington, D.C. She married William Sinclair on December 9, 1865, and their daughter Bell was born around 1868. Her husband served as an officer in the United States Army. She accompanied him to several of his postings. He served as quartermaster of the United States Military Academy from September 1865 until September 1868, and he spent the next three years in Kansas and Nebraska. By 1870, they owned $1,000 of personal property, and they employed at least one white domestic servant.
They were stationed at Fort Hamilton, New York, from November 1872 until December 1881 and then at the Mount Vernon Barracks in Alabama from June 1885 until May 1889. Her husband commanded Fort Warren in Massachusetts from 1889 until September 1895, and he retired from the army in February 1899. Her husband died on October 3, 1905, and her daughter died in July 1907. By 1910, she was living in Washington, D.C. She died there of chronic myocarditis on December 9, 1916.