[3] She was born in Dublin, Ireland to Raphael Walsh, a furniture designer and manufacturer from Navan, County Meath.

In 1975, when Walsh was 16, she began studies at the Dún Laoghaire Institute of Art, Design and Technology in Dublin.

She then transitioned into television work throughout the 1990s,[8] including episodes of The Bill (1991–1994), Doctor Finlay (1993), Roughnecks (1995), and Trial & Retribution (1997–2002).

[12] Throughout the 2000s and early 2010s, Walsh also continued working in television, directing series and television films such as the BAFTA TV Award-nominated Fingersmith (2005); the BBC One film Sinners (2007);[13] The Fifth Woman, a feature-length episode of the BBC series Wallander, starring Kenneth Branagh (2010); and Room at the Top (2012), which earned her a BAFTA TV Award in 2013 for Best Mini-Series.

[17] As someone who studied painting herself,[8] Walsh was drawn to the simplicity and beauty in Lewis's work.