Hi
Most of my research has been concentrated in Canada and the United States. The majority of Diette's that I have found in the US were originally GUILLET. This was the original French name.
To help you find out more, do you know where in France your parents are from?
The names of your paternal grandparents and where they lived in France?
That would help you get started in finding out if there are others out there that are related to you.
Hope this helps.