Reference request about St. John Vianney and the Miraculous Medal? I have come across on a couple of websites (one a blog), but never in a book, the following conversation between the Cure d'Ars and one of his penitents:
``Do you remember that you went to a ball on such-and-such occasion?
``Yes, I remember.
``Do you remember that at a certain moment a handsome young man entered the ballroom? He was quite elegant, appeared very upright and danced with several young ladies?
``Yes, I do.
``Do you recall that you had a great desire to dance with him?
``I recall that.
``Do you recollect that you became sad because he didn’t ask you to dance?
``Yes, I do.
``Do you remember that by chance you looked down at his feet and saw a strange blue light coming from them?
``Yes. I remember.
``That young man was none other than the devil who had taken that shape to tempt several of the young women there. He was unable to approach you because you are a Daughter of Mary protected by her, and you were wearing the Miraculous Medal.
I have never come across a legitimate reference for this conversation.
The two sites that I have seen this conversation recounted are:

St. John Baptist Vianney, August 9
St. John Vianney

My Question is: Can anyone who may be familiar with St. John Vianney and the Miraculous Medal provide me with a valid citation for this conversation? The aforementioned sites provide no reference. Thank you.
Question Pertaining to St. John Vianney and the Miraculous Medal
I have a great devotion to St. John Vianney and have read the works on the Curé D'Ars by Mgr. Francis Trochu, the procurator of his cause in French.
If you can locate one of the first published works that were written by him for the beatification and/or canonization of Jean-Marie Baptiste Vianney you would find your references desired. Possibly later works could include the references you desire.
The procurators must publish the written works of his investigation which are heavily annotated with notes and sources, for the Sacred Congregation for the Causes of Saints.
If you are lucky, you may possibly find a biography about the Curé D'Ars: St. Jean-Marie Baptiste Vianney in English by the same author. Do not look at the abridged biographies of him. The greater number of pages, the greater the possibility that the notes you are looking for with be in that particular biographical works!
I know to be certain of what I am saying because I have personally read this original work on Curé D'Ars, with the very notes and references you are desiring because I read this work some 30 years ago in French. If fact, at times I found the notes more interesting than the actual biography itself.

The Curé D'Ars: St. Jean-Marie Baptiste Vianney by Mgr. Francis Trochu. This image is given as an example of Mgr. Trochu’s works only!