Nice work.
Yes, she could have been present too if her mother was with her brother (Jimmie Johnston). Belle Johnston would have been about 5 in 1864.
I found a reference that she was connected (genealogically) directly to Confederates Gen. Joe Johnston and Gen. R. E. Lee. I figure that would make you a hot shot in the UDCV in Virginia as she reportedly was. And besides her father being a hero of the U.S. Navy during the war.