Is there any evidence that Chrysi endorses the title used by whoever wrote that part of the Wikipedia article?
Given that other family members, past and present, do not use "Prince(ss) X of Greece and Denmark", but rather "Prince(ss) X of Greece", I doubt it.
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Regarding the above criticisms of the family’s choice of surname:
From a pan-European perspective, the most traditionally royal surname choices for the family would be “of Greece” or “of Glücksburg”.
Originally, most European royalty and nobility did not have hereditary family names. The general pattern was that whenever a royal or noble house (family) or person required a “surname”, they would simply be called by the name of the territory or castle where they lived and/or ruled.
European royal families who partially continue in this older tradition include the Belgian, Danish, Luxembourgian and Monegasque reigning families, whose members use “of Belgium”, “to/of Denmark”, “of Luxembourg” and “of Monaco” as unofficial surnames in their daily lives, and the British royal family, which uses “Windsor” [Castle] as its official house name.
If the Greek former royal family observed this older tradition, “of Greece” would be the natural choice.
As time went on, most European royal and noble families, adopted hereditary family names. This typically involved the territorial or castle names their ancestors had used, as mentioned above, but the name became hereditary, rather than linked to the real ownership of the territory or castle.
European royal families who follow this newer tradition include the Spanish, Luxembourgian, Dutch, Belgian, Danish and Norwegian royal houses. The legal surnames “of Bourbon” (a former duchy in France), “of Nassau” (a former duchy in Germany), “of Orange-Nassau” (Orange is a former principality in France)” and “of Saxe-Coburg” (a former duchy in Germany)”, and the official house name “of Glücksborg/Glücksburg”, all refer to territories governed by ancestors of those royal families.
If the Greek former royal family observed this newer tradition, “of Glücksburg” (which is the official house name of the
Danish and
Norwegian royal families) would be the natural choice.
So the choice of “of Greece” as a surname was in fact one of the most “royal” surname choices they could have made.
Some may object that their chosen surname was not exactly “of Greece” (tis Ellados), but “of Greece” translated into French (De Grèce). That is true. But
as they pointed out, they did this to be consistent with their deceased cousin Michel De Grèce, who held both Greek and French citizenship and decided to use the same surname in Greece that he used in France. In this way, all the male-line members of the family have the same legal surname.
There is precedent for this in European royal circles as well. The children of Princess Irene of the Netherlands use the French “de Bourbon de Parme” as their legal surname in the Netherlands instead of translating it to the Dutch “van Bourbon van Parma”. This was done to maintain consistency with their relatives in the grand-ducal family of Luxembourg, whose members held the subsidiary title “Prince(sse) de Bourbon de Parme”.
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Could you share a link where the book can be seen? I would like to see just how Marie-Chantal wrote her name. 
