Clara Barton was born on December 25, 1821, in Oxford, Massachusetts. She became a teacher, worked in the U.S. Patent Office and was an independent nurse during the Civil War. While visiting Europe, she worked with a relief organization known as the International Red Cross, and lobbied for an American branch when she returned home. The American Red Cross was founded in 1881, and Barton served as its first president. See: http://www.biography.com/people/clara-barton-9200960
I assume you are asking about a WOMAN, since the only history of girls helping during the civil war are the handful that disguised themselves as boys so they could join the fighting. The most famous women contributing to the civil war are: ---Dorothea Dix, Head of and recruiter of women as Union nurses. To avoid social disapproval of women tending wounded men's bodies, she insisted all nurses must be over 30, be very plain looking, wear only dark colors, and wear no ribbons or frills. ---Harriet Tubman, led 300 slaves to freedom prior to the war, and during the war appointed by Mass. governor as Union nurse, teacher to escaped slaves, and as a spy for the Union (when she went behind rebel lines as a battlefield nurse). ---Clara Barton, independent nurse during civil war, later made head of nurses at an army fort hospital. Started an American branch of the European Red Cross after the war, about 1881. ..... Couldn't find anything historical about a "Molly Hatcher", at all, except an old song lyric. There was a "Molly Pitcher" during the Revolutionary war, but that was a nickname for all girls who brought pitchers of water onto the battlefield. A soldier would shout "Molly! Pitcher!" And a girl would carry water out, either for drinking or to cool down the cannons that were dangerously overheating. I would not be surprised if the same thing happened during the Civil War, since women and boys carried water then, too, for the same reasons.