Fairy Queen

The daughter of a vicar from Ashbourne in England, Eleanor Jourdain had been walking down a grass path between trees in the park of Versailles in 1902, when she heard French voices in animated conversation behind her. She turns to see nodbody, but as the group closes on her, she feels her 'room being taken up by a woman talking in old French'. Who was this woman she grows to look like, who would appear to her dressed in white?