A Laoise,What CD or recording did you hear Mairéad singing Mo Ghile Mear? I can't find it on any of the recordings I have.
If you're looking at the lyrics and listening to the song, the pronounciation she is using might be leading you to think that she's singing different words than the ones you have. Mo Ghile Mear is a song from the south, and Mairéad is from Co. Donegal in the North. The differences in the dialects of Irish spoken in the south and the north are very great.
Áine