Princess is a regal rank and the feminine equivalent of prince (from Latin princeps, meaning principal citizen). Most often, the term has been used for the consort of a prince, or for the daughter of a king or prince.
From 1917, therefore, his daughter was known as "Lady Louise Mountbatten". Her mother was Princess Victoria of Hesse and by Rhine , a granddaughter of Queen Victoria . Louise was a sister of Louis Mountbatten, 1st Earl Mountbatten of Burma , and of Princess Alice of Battenberg , who was the mother of Prince Philip, Duke of Edinburgh .