Complex sentence: She finished school early, graduating from high school at the age of 15, completing her Bachelor's degree in 3 years, her Masters in 2.5 years and her Ph.D. at the age of 24, which was awarded to her in May 1990.
Split into simpler sentences: She finished school rather early, graduating from high school at the age of 15, completing her Bachelor's degree in 3 years and her Masters in 2.5 years. She also finished her Ph.D. at the age of 24, which was awarded to her in May 1990.