Complex sentence: Although warned to give up her career, Washington ignores her health issues and selflessly assures the Duke that she is healthy enough to perform, which ultimately leads to her dancing herself to death to Ellington's tune, "Black and Tan Fantasy".
Split into simpler sentences: Although warned to give up dancing, Washington assures the Duke that she is healthy enough to perform. But she dances to her death to Ellington's tune, "Black and Tan Fantasy".