Complex sentence: Margaret Leahy (17 August 1902--17 February 1967) was a British actress, born in London, who won a beauty contest and who made only one film in her very short-lived film career.
Split into simpler sentences: Margaret Leahy (17 August 1902--17 February 1967) was a British actress. After winning a beauty contest, Leahy went on to make only one film in her very short-lived film career.