Complex sentence: She had one of the best rookie seasons ever recorded in the history of gymnastics, winning the all-around at the American Cup, Pan American Games, US National Championships, and World Championships all in her first year as a senior gymnast.
Split into simpler sentences: She had one of the best rookie seasons ever recorded in the history of gymnastics. She won the all-around at the American Cup, Pan American Games, US National Championships, and World Championships all in her first year as a senior gymnast.