Marcella is a former member of Offaly County Council, serving from 1999- 2009. She has also been Chairperson of the Midlands Regional Authority and Chairperson of the Birr Theatre and Arts Centre. She was appointed Chairperson of the Oireachtas Committee on Jobs, Enterprise and Innovation on July 22, 2014.
Marcella was also a Director of West Offaly Enterprise Fund Ltd and a member of the West Offaly Community Forum. Mother to two children, Marcella enjoys going to the theatre. Her favourite playwright is Martin McDonagh. She is also a fan of The West Wing television series.