Thanks, Paul, for responding to my query with this information. You've given me a new set of leads to explore, and I truly appreciate your help. This Rachel Mann could be related to the Cook family in DC and/or the Strange families in VA, PA, and OH.

VA-born Rachael Mann in DC may be related to Civil War soldiers Aaron and John Mann who served in US Colored Infantry regiments organized in Philadelphia and the District of Columbia. Other relatives might include VA-born DC residents, Henry (born c. 1817) and Joseph (born c. 1818). Henry Mann relocated with his wife Alice by 1880 to Cleveland, OH, where other members of the DC-based Mann family had migrated around 1860.