Her credits include Miss Julie (1999), Janice Beard 45 WPM (1999), When Brendan Met Trudy (2000), The Magdalene Sisters (2002), Pure Mule (2005), Eden (2008), The End (2008), Catastrophe (2015), The Children Act (2017), Maze (2017), Wolf (2021), and Ann (2022).

[1] A young Eileen began to attend theatre workshops and her first break came when, as a student, in 1996, she landed the role of Runt in the stage version of Disco Pigs, alongside Cillian Murphy, who played her friend.

[2] In 1999, she played the titular character in Janice Beard 45 WPM, alongside Rhys Ifans, Patsy Kensit and Eddie Marsan.

[5] In 2002, she played the role of Crispina in The Magdalene Sisters, where her character was beaten and humiliated by nuns, forced to strip, and sexually abused by a Roman Catholic Priest.

[2] Her performance earned her a nomination for British Supporting Actress of the Year at the 2002 London Film Critics' Circle Awards.