Min syster och jag (1950)

The rich, aristocratic Katarina Hassel have an architect renovate her mansion. Katarina fall in love with the young architect, Gunnar Stenwall. Alas, he doesn't fall in love with her. But perhaps if Gunnar would meet her identical sister, who works in Stockholm as a waitress, he would fall in love with her instead? So Katarina travels to Stockholm to act as her non-existing sister.