I have a BUNCH of her music, almost all of it. Sadly I don't have The Celts album, which it probably is from. But perhaps some of these?:
The Celts Tempus Vernum Deora Ar Mo Chroi (Actually, this one doubtful, not really great beat) Pax Deorum Athair ar Neamh (doubtful too, but eh) Cursum Perficio Maybe even the Gaelic version of Book of Days?
These are the ones that stuck out of my many songs, but like I said, might look into the Celts album as well Hopefully that was useful anyway
I wish I can help but I can't. My girlfriend listens to that stuff and I hear it in the background while I'm doing something. If I knew the titles of some I can probably help but I don't. I would suggest going to youtube I usually find songs that way! Hope you find the song!