O'Neill was born in Japan to a Japanese mother, Sumie, and a New Zealand father, Chris, a professional rugby player. She has two younger brothers. O'Neill started dancing when she was three years old. From 1998 to 2007, O'Neill studied at the Kishibe Ballet Studio in Tokyo, Japan. When she turned eight, she moved with her family to
Auckland, New Zealand. In 2011 she graduated as dux of the ballet school. ==Career==