What does the change of the old woman to a young girl with the walk of a queen signify?
Cathleen ni Houlihan by William Butler Yeats is an allegory of Ireland, with the mysterious old woman representing Ireland herself. The country is first represented as an old women for several reasons. First, Yeats was interested in Irish folklore and the ancient traditions of the Celts. The age, wisdom, and mystery of Cathleen ni Houlihan suggests the ancient Celts, who lived in Ireland before the conquest by the British, and Cathleen's quest for her green acres the desire of the Irish to reclaim their sovereignty over their historic lands. Her old age, though, has a second signification, that of being tired and downtrodden, only able to sing of her lost glory rather than to reclaim it. While this singing is portrayed positively -- the songs of Cathleen represent the Irish artistic and poetic tradition which Yeats greatly admired -- nonetheless the image is one of impotence.
When Michael Gillane joins the rebellion at the behest of Cathleen, she appears to regain her youth and power. This image is one of Ireland as the proud and independent country Ireland might become if freed of British oppression, something for Yeats that in part depends on the liberation of the spirit of the peasants (represented by the Gillanes) close to the Irish soil, rather than just the intelligentsia of Dublin.