Mary was elected to Dáil Éireann on her first attempt in the 2011 General Election. She had previously served on Dún Laoghaire Rathdown County Council after being elected on her first attempt in June 2004 and re-elected in June 2009. Mary is a qualified teacher and before her election was Principal of the Harold School Glasthule, a busy mixed Catholic school with 500 pupils. During her time there, Mary successfully managed the amalgamation of St. Joseph's Boys School and Harold Convent Girls' School. Mary will prioritise education issues during her time in the Dáil. Mary is extremely supportive of local business and enterprise.
She has consistently fought against increases in commercial rates in the Council in order to help keep the cost of doing business down.