Belle Boyd...via Civil War Women's blog

Only 17 years old when the War began, by early 1862 Belle Boyd of Martinsburg (now West Virginia) and her activities were well known to the Union Army and the press, who dubbed her La Belle Rebelle. While visiting relatives whose home in Front Royal, Virginia was being used as a Union headquarters, Boyd learned that Union General Nathaniel Banks' forces had been ordered to march. 

She rode fifteen miles to inform Confederate General Stonewall Jackson who was nearby in the Shenandoah Valley. She returned home under cover of darkness. Several weeks later, on May 23, 1862, when she realized Jackson was about to attack Front Royal, she ran onto the battlefield to provide the General with last minute information about the Union troop dispositions. Jackson captured the town and acknowledged her contribution and her bravery in a personal note.

Boyd was arrested several times, but managed to avoid incarceration until July 29, 1862, when she was imprisoned in Old Capitol Prison in Washington, DC, but was released after a month. She was arrested again in July 1863, after which she devised a unique method of communicating with her supporters outside. They shot rubber balls into her cell with a bow and arrow; she then enclosed messages inside the balls and threw them back. 

In December 1863 Boyd was released and banished to the South. She sailed for England on May 8, 1864, but was arrested again as a Confederate courier. She finally escaped to Canada with the help of a Union naval officer, Lieutenant Sam Hardinge, and eventually made her way to England where she and Hardinge were married. Boyd later wrote of her wartime activities, "I allowed but one thought to keep possession of my mind - the thought that I was doing all a woman could do for her country's cause."