Every time a story is retold, it is modified to some extent
Before our modern time, ideas and stories were kept alive through word of mouth and certain writings, which led to much freedom to interpretation among listeners and digesters. In this sense, no form of a fairy tale is purely "traditional."
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We often think of "traditional" fairy tales as stories written by the great European writers: the Brothers Grimm of Germany, Poet Basile of Italy, or members of the French courts like Beaumont and Perrault. But to your dismay, even these great writers created adaptations of stories created by those before them! Looking at Cinderella, one of the oldest fairy tales, the initial "traditional" princess and slipper story came from the Greeks who shared stories of a slave girl, Rhodopis, whose sandal was dropped into the lap of the King of Egypt by Zeus. The King then searched for the owner of the slipper and made Rhodopis his queen. In the Grimm adaptation, Rhodopis was named "Aschenputtel" (Ash girl) and has a magical tree that hands her ball gowns and gold slippers on command! Even the material of the slipper has been disputed due to so many different accounts of the story. In French versions, the slippers are thought to be made of fur or "vair", but there is speculation that the glass slipper aspect of the story was formulated due to the french word for glass being "verre", which could be confused with "vair" over many generations. In every iteration, the writers adapted the parameters of the story to suit their audience and society and the question remains, what is the "traditional" fairy tale?
Although the stories are naturally written in different ways/change over time, the essence of the stories are not changing with each iteration. Only semantic things such as the fur vs. glass slipper, etc. are changing, which ultimately have minimal effects on the actual lessons learned through the fairytale. Therefore, this does not qualify as being modified in the same way that "rewriting" the fairy tale, where the entire concept is altered, would.