Complex sentence: As a speed skater, she competed in the 1972 Winter Olympics where she finished 7th in the 1500m--she was fourteen years old at the time, making her the youngest American female Winter Olympian.
Split into simpler sentences: As a speed skater, she competed in the 1972 Winter Olympics, where she finished 7th in the 1500m. She was fourteen years old at the time, making her the youngest American female Winter Olympian.