Born in Northern Ireland, Mary studied at The Royal Academy of Music where she was elected a Fellow in 2019.

Mary was appointed as a company principal with English National Opera where her roles included Susanna, Pamina, Dalinda, Atalanta, Belinda, The Fairy Queen (including performances in the Gran Teatre del Liceu in Barcelona) and Lucia in David McVicar’s production of The Rape of Lucretia for ENO and the Aldeburgh Festival, which was also broadcast on BBC 2. Other roles include Carolina in The Secret Marriage for Opera North, Ismene in Mitridate for the Classical Opera Company and Piacere in Il trionfo del Tempo e de Disinganno for The Early Opera Company, Gilda, Micaela and Nedda. She also performed Poulenc’s Gloria at The Royal Opera House.

An experienced oratorio and concert soloist, Mary has performed Mozart's Requiem and Bach's St Matthew Passion with the City of London Sinfonia, Vivaldi's La Senna Festeggiante with The King's Consort in The Netherlands and Spain, Purcell's Dido and Aeneas, Handel's Gloria with the Irish Chamber Orchestra and Bach's St John Passion with the Orchestra of the Age of Enlightenment. In addition she has performed Mozart's C Minor Mass, Bach's Magnificat and Vivaldi's Gloria with the English Chamber Orchestra, Handel's Messiah with the Bournemouth Symphony Orchestra, Orf's Carmina Burana with the Royal Scottish National Orchestra and Handel's Athalia with the Scottish Chamber Orchestra.

Engagements have also included performances of Handel's Alexander's Feast with the Music of the Baroque in Chicago, Mozart's Requiem with the Halle, Mozart's Regina Coeli with The Academy of Ancient Music, Brahm's Requiem with the Dutch Radio Symphony Orchestra, Hansel and Gretel and Mendelssohn's A Midsummer Nights Dream for the BBC Proms, Mozart's Exsultate Jubilate with the Tenerife Symphony Orchestra, Faure's Requiem with the Northern Sinfonia, Handel's Messiah with the Brno Philharmonic, Britten's Les Illuminations with the Israel Camerata, Mahler’s 4th Symphony with the RTE Symphony Orchestra and Haydn’s Creation with The Prague Philharmonic.

Mary has collaborated with conductors such as Sir Richard Hickox, Jakub Hrusa, Nicholas McGegan, Thierry Fischer, Christian Curnyn, Jane Glover, Takuo Yuasa, Paul Daniel, Harry Christophers, Harry Bicket and John Nelson.

An experienced recitalist, Mary has given concerts at the Wigmore Hall and also undertaken a recital tour of Argentina to great critical acclaim. Her recordings include Vivaldi Cantatas with The Band of Instruments, Mendelssohn's Symphony No. 2 and songs by Georg Schumann.

In 2015, Mary became a Professor of Singing at the Academy.