Wallace was born in Dublin in 1959. She was educated at the Loreto Convents in Balbriggan and North Great Georges Street, Dublin and the College of Commerce, Rathmines, where she received a diploma in Hospital and Health Services Administration. Following this, she went on to work as a Personnel Executive in Blanchardstown Hospital.
In February 2006, Wallace rejoined the junior ministerial team as Minister of State at the Department of Agriculture and Food with special responsibility for Forestry.[4][5] Her promotion caused some surprise as Seán Haughey had been the front-runner for promotion, while Wallace's name had not even been mentioned.[citation needed] She was reappointed to the same responsibility the following year on the formation of a new government.[6]
In May 2008, after Brian Cowen succeeded Ahern as Taoiseach, she was appointed as Minister of State at the Department of Health and Children with special responsibility for Health Promotion and Food Safety.[7][8] She lost her position as Minister of State in a reshuffle on 21 April 2009, when Cowen reduced the number of Ministers of State from 20 to 15.[9]