Very interesting story.
Evidently she got special (and unique) permission to join her husband in the army, with the specific role of running a small 'general store' out of a wagon, but in fact she fought in battle, risked her life several times, and famously saved the lives of many men:
Just as a number of Union regiments were getting into their battle positions on the morning of March 14, members of the 5th Rhode Island came out of a clump of woods from an unexpected direction, giving the appearance that they might be a disguised rebel force preparing to attack. Realizing that a misunderstanding might lead the regiments already in line to open fire, and with no fear for her own safety, tradition has it that Brownell—who had moved to the rear as ordered—ran forward into clear view of those already in place, carrying her regiment's flag and waving it wildly until the 5th Rhode Island soldiers' identity became clear to surrounding regiments.[5] --WP
What a gal and what a braveheart. <3