Irish born, Rebecca grew up in South County Dublin. Daughter of Stephen and Veronica Jane O'Mara, sister of Jason and Stephen James. She attended Holy Child School, Killiney and later got her degree in Drama and Theatre at Trinity College Dublin. On graduating, she moved to London and worked in film production for some years. In 2004, she began her classical acting training at LAMDA. She works as an actress in British and Irish theatre, television and film. She also works as a voice over artist.