Who is Bridget O'Shea from Behind Rebel Lines: The Incredible Story of Emma Edmonds, Civil War Spy and what is their importance?

Emma took on the identity of Bridget O'Shea during an undercover mission. Emma wore Mrs. Butler's clothes and put a pillow around her middle in orer to take on the appearance of an older, matronly woman. She dusted her dark hair with flour to make it look like gray hair.