Tierney started dancing from a very young age, studying ballet primarily and attending her mums school, Lawlor School of Dance. At the age of 16, she joined CAT at The Place and after two years of training there, she was accepted onto the degree course at Rambert School. During her time at school, Tierney choreographed and performed in many student pieces and worked with choreographers Monique Jonas, Julie Cunningham and Connor Scott. She was also the Conservatoire for Dance and Drama student governor during her final year.
Since graduating, Tierney has been teaching ballet and contemporary alongside studying for the Royal Ballet School Diploma of Dance Teaching. She has also worked closely with National Youth Ballet, directing their Dancers Development Program in August 2022 and as a Beyond Ballet young artist.