She is known for her work with the short-lived, but very highly regarded Skara Brae and her collaborations with her sister Tríona Ní Dhomhnaill, as well as other traditional musicians.

[1] With her sister, Moya Brennan and Mairéad Ní Mhaonaigh, she is part of the Celtic supergroup T with the Maggies, which has released a CD in October 2010.

Her father's family were native Irish-speakers from Rann na Feirste, County Donegal and she was therefore brought up speaking the language, along with her sister Tríona and brothers Éamonn, Mícheál and Conall.

The other members of the group were Mícheál Ó Domhnaill (her brother), Tríona Ní Dhomhnaill (her sister) and Dáithí Sproule from Derry.

She has also previously used the spelling "Maighréad", but has removed the accented e. Ní Dhomhnaill studied nursing and raised a family, giving up music for a while.