I have found more information about the actions of Betty Herndon Maury's husband, William Arden Maury, during the opening months of the American Civil War. He was involved in procuring land patents and certificates for land patents, as revealed by seizure of contraband mail by the U.S. Government in December 1861. See The War of the Rebellion, Series II Volume II, page 1309. This link will take you to page 1307; Will is mentioned on page 1309.
Note that the text of The War of the Rebellion text is unclear about the relationship of Rutson Maury to Betty's father - or to her husband. The Rutson Maury who was arrested for mail and document smuggling in November 1861 was most likely the Rutson Maury born in 1835. His brother, another Matthew Fontaine Maury, born in 1834, was also arrested and imprisoned for mail and document smuggling. On November 24, 1861 Betty reports the arrest of "Fontaine Maury, Nannie's old sweetheart . . ."
From Betty's diary it appears that Will was not sharing with her much about what he was doing.