Mary O'Donnell began her harp studies with the late Sr. Eugene McCabe at Mount Sackville School in Dublin and she later studied with Fiona Norwood, Sebastien Lipman and attended masterclasses with the renowned harpist and teacher Edward Witsenberg. In 1992 she was awarded an Entrance Exhibition to Trinity College Dublin and graduated with an honours degree in Music in 1996. As an undergraduate, she completed her ARIAM in Irish Harp and LTCL in Concert Harp performance. She also holds a Higher Diploma in Education and a Masters in Musicology (with a specialism in Ethnomusicology) from University College Dublin. In 2007, Mary was awarded an IRCHSS Government of Ireland scholarship to continue doctoral studies at the University of Limerick (UL) on the social, political and cultural history of the Irish harp and its patronage from 1790 to 1845. In 2011 she was awarded an IRCHSS Government of Ireland Postdoctoral Fellowship to prepare her doctoral dissertation for publication at the Irish World Academy of Music and Dance under the mentorship of Professor Mícheál Ó Súilleabháin.
In 2012, Mary was appointed Chair of Ionad na Cruite, the Irish Harp Research Centre at the Irish World Academy of Music and Dance, UL and in 2013, she was awarded a Dobbin Scholarship by the Ireland Canada University Foundation (ICUF). Her first monograph, Ireland's Harp: The Shaping of Irish Identity c.1770-1880 was published by UCD Press in 2014. Mary Louise was awarded a Fulbright Scholarship in 2019 to undertake research at the Falvey Memorial Library at Villanova University on the significance of the Irish harp as a political and cultural emblem of identification among Irish emigrants in the United States from 1780 to 1930. The fruits of her research on the employment of the harp as a visual symbol, literary trope and musical instrument will be incorporated into a book on the history of the Irish harp symbol from its earliest use as a colonial symbol up to the present day. The book will be published in 2022 to mark the centenary of the foundation of the Irish Free State and the adoption of the Irish harp as its official emblem.
She has won many prizes at competitions throughout the country and at the Dublin Feis Ceoil, she has won first prizes in all Junior and Senior Irish and Concert Harp competitions, as well as prizes in singing and composition (Dr. Annie Patterson Medal). Mary is a former member of the National Youth Orchestra, RTE Cor na nOg, Belfast Harp Orchestra and has performed with many ensembles and orchestras (amateur and professional) throughout the country. She has appeared on RTE, BBC, CNN, and NBC and has toured extensively with different groups throughout Europe, North America, Africa and most recently to Asia. Mary began lecturing at St Patrick's College, Drumcondra in 2005 and was a tutor and lecturer at the University of Limerick from 2006. She worked as an examiner with the Royal Irish Academy of Music, Dublin. from 1998 to 2010.