Mitchell was born on June 2, 1890, in Atlantic Highlands, New Jersey. She attended school at the Mary Institute in Atlantic Highlands and graduated from Vassar in 1912. She continued her education by earning a master's degree in social work at the Washington University in St. Louis George Warren Brown School of Social Work. Her Master's thesis was entitled The Immigrant in St. Louis. She began doctoral work at Johns Hopkins but did not complete her studies there. In 1914, she worked as the YWCA's Field Secretary for the Immigration and Foreign Community Program of the YWCA.
