Patricia Walters
According to her mini biography here, Patricia Walters (Harriet in the film) was: "Found in Bengal in a casting call by director Jean Renoir, Walters was the daughter of a man on the staff of one of the local industrial concerns, according to Renoir's memoir."
Also on her page it says she was born in Illinois in 1929, the daughter of American comedian Bert Wheeler. This would make her 22 in the film. Possible, but unlikely. And American? Highly doubtful given her accent, which in fact sounds slightly South African if anything.