Ernst Lubitsch The Smiling Lieutenant Blu Ray from 1931.
A simple wink, intended by Austrian palace guard Lieutenant Nikolaus von Preyn (Maurice Chevalier) for girlfriend, Franzi (Claudette Colbert), is accidentally intercepted--and misread--by the visiting Princess Anna (Miriam Hopkins). As a result, the soldier has no choice but to marry the royal lady and move with her to the neighbouring kingdom of Flausenthurm. His girlfriend follows to continue the romance and, subversively, give Princess Anna tips on how to keep her husband satisfied