Gillian began dancing ballet at the age of five. She studied intensively and performed extensively until she was eleven, when she quit and started to explore other forms, such as musical theatre and circus. She trained as an aerialist for over five years as a teenager, and continued dancing casually.
She majored in dance at Columbia University in New York, where she studied extensively with long-term Graham company member, Donlin Foreman, and learned other forms, such as tap and jazz. She also studied abroad for a year in Paris, where she studied under Anne Debaecker at Paris 7 Denis Diderot and other studios.
She continued dancing during her three years in Cambodia, mostly with the Central School of Ballet in Phnom Penh. Upon her move to Seoul, she started training with contemporary company Trust Dance Theatre and danced as a guest dancer with Second Nature Dance Company. In November 2016, she was named member of Second Nature.