I guess it depends on how you look at the issue. Following the abdication of Wilhelm II on November 9, 1918 the German nobility and royalty as legally defined classes were abolished on August 11, 1919 with the promulgation of the Weimar Constitution, under which all Germans were made equal before the law, and the legal rights and privileges, and all following German Houses, titles, insignia and ranks of nobility were abolished. So legally the title of Queen was abolished and the title were then held in pretense.

I think there needs to be a distinction between a Queen Consort who was a dowager, their royal husbands had passed away, a Queen Consort who’s husband had lost the throne but the monarchy was still extant, and then there are Queen Consorts from countries where the monarchy has been abolished.

For example I personally have no problem as a monarchist recognizing the titles of King Constantine II and Queen Anne Marie of the Hellenes but in Greece those titles no longer exist under the law.

My question is, how do foreign courts, such as the United Kingdom of Denmark, for example, who have diplomatic relationships with Greece handle Constantine and Anne Marie’s titles? Does Denmark take an official stance on the subject and recognize Queen Margarethe II’s sister as Queen even when Greece does not? Does that create any diplomatic tension?