Mmario, I have the record (mea culpa!) and I believe I remember the verse about the Albigensians that Peter T quoted. The nun's name meant "Sister Smile." I heard (may be fakelore) that the success went to her head and she left the convent to try her hand as a singer, whereupon nobody liked her singing anymore.... Part of its charm, actually, was the lighthearted innocence of the songs. Image is all.... Leaving the convent would have ruined her image if it's true.
Anyway, "Dominique" is a song singing the praises of st. Dominic. I guess they were Dominican nuns.