Padraic Colum a member of the Gaelic League and the first board of the Abbey Theatre, was also a regular user of the National Library of Ireland where he first met James Joyce and formed a lifelong friendship.

He also collected Irish folk songs, including She Moved Through the Fair in Donegal for which it is has been said Colum wrote most of the words, with the musicologist Herbert Hughes and this version was
published by Boosey & Hawkes in London in 1909 in a work entitled Irish country songs.

These lyrics were later published in Colum's 1922 book Wild earth: and other poems (though the book doesn't mention their traditional origin)

It all depends on your definition of 'traditional' I suppose - and whether you think it really matters.