The Daredevil - Maria Thompson Daviess

Roberta, daughter of an American soldier and a French marquise, is returning to the childhood home of her father after his death in the Great War. Upon reaching New York she realizes that her Uncle, a woman-hater, has confused the genders of her and her small crippled brother. In order to please her Uncle and ensure medical treatment for Pierre, she becomes "Robert", his nephew. In her new identity she secures supplies for France, has many hilarious close-calls, and manages to fall in love with the Governor. - Summary by LikeManyWaters