Her parents separated when she was an infant, and she was predominantly raised by her mother while visiting her father on weekends.
McCormack left school at 14 to be homeschooled due to bullying and completed her Leaving Cert at a private college.
[3][4] Signed with Morgan the Agency, McCormack began her modeling career when she was 14, with gigs for The Bridge, Arnotts and Life Style Sports.
[6] In December 2020, it was reported that McCormack would appear in the second season of Netflix adaptation of Andrzej Sapkowski's The Witcher as the mysterious W.[7][8] She reprised her role as Róisín from the 2016 short film Lily in its 2021 feature version Who We Love, marking McCormack's feature film debut.
In 2022, she played Sophie in the film The Magic Flute and made a guest appearance in the Disney+ series Willow.