The Good:
… Picture?
The Bad:
Zero Online Activity
Conclusion:
Mary Lou McDonald is not using online media in her campaign. In fact there is only one page about her really, and this is the text from it:

Mary Lou McDonald is a member of the Sinn Féin Ard Chomhairle and MEP for Dublin.

She is married to Martin Lanigan and they have a baby daughter. Educated in Trinity College, Dublin, the University of Limerick and Dublin City University Mary Lou has studied English Literature, European Integration Studies and Human Resource Management.

She previously worked as a consultant for the Irish Productivity Centre, a researcher for the Institute of European Affairs and a trainer in the trade union sponsored Partnership Unit of the Educational and Training Services Trust. She previously worked for the party in co-ordinating the work of Sinn Féin elected representatives across the island.

From: http://www.sinnfein.ie/euteam/candidate/mcdonald