Rosa Nienau first met Hitler alongside her mother in 1932 and was part of a group which visited the Nazi leader on his birthday in 1933, in the Bavarian town of Obersalzberg.
When Hitler found out that Rosa shared his birthday, he invited her up to his mountain residence, the Berghof, for strawberries and cream.
Rosa’s maternal grandmother was of Jewish origin - and under Nazi law, one Jewish grandparent was enough to consider Rosa to be suspect (under Jewish law, which is matrilineal, Rosa was considered completely Jewish).
However, despite being responsible for the murder of six million Jews in the coming years, Hitler refused to break the relationship.
As described in Mr Hoffman's memoir, 'Hitler, As I Saw Him', the dictator overruled initial attempts by his personal secretary, Martin Bormann, to break off his relationship with Rosa.
The dictator said: "There are people who have a true talent for spoiling my every joy."
However, by 1938 Rosa was banned from making contact from Hitler. She died from spinal polio five years later.
The photo is to be sold by Alexander Historical Auctions in Chesapeake, Maryland on November 13.
Bill Panagopulos, the auctioneer, described the picture as a “never-before publicly seen piece.
“Hitler was very often photographed with children for propaganda purposes. The shocking thing about this piece is it seems he had a genuine affinity for the young girl.
“The Bundesarchive retains 17 letters from her to Hitler and aide Wilhelm Bruckner between 1935 and 1938.”
