Cronin O'Reilly grew up in County Kerry, Ireland, and attended the Killorglin Intermediate School.
She went on to further education at St. John's Central College in Cork, and did work experience at Ardmore Studios, in special effects, editing, and as a camera operator.
[2][3] Cronin O'Reilly was nominated for an Academy Award for her graduation short film, Head Over Heels.
[2] Of God's Creatures (2022), Cronin O'Reilly has said "I grew up in a small fishing village in Kerry, I'm from a family of fishermen, and there were certain things I wanted to explore that exist within my world.
I was also hearing different stories of women in particular, making allegations of sexual assault and how they were being treated by their own communities, their own neighbors".