Absender Grossherzogin d'Luxemburg in 1916

Mourning Cover in the Hand of
G.D. Marie-Adélaïde

Who was Grand Duchess Marie-Adélaïde mourning when she posted this cover from Schloss Berg at Colmar-Berg on December 4, 1916,  to the Baroness Ritter in Munich, Germany?  Perhaps I'll find the answer in Edith O'Shaughnessy's detailed biography of the Grand Duchess, or maybe a reader of this blog will offer a suggestion.

Marie-Adélaïde's distinctive handwriting sometimes perplexed postal clerks.  Here someone, after deciphering the cover's destination, has written München in colored pencil across the front with strong underscoring!

Update

Indeed, Edith O'Shaughnessy, in her fine biography, Marie Adelaide: Grand Duchess of Luxemburg Duchess of Nassau (1921: Harrison Smith, New York), tells us that it was Marie-Adélaïde's paternal grandmother, Adelheid-Marie of Anhalt-Dessau, for whom Marie-Adélaïde was in mourning when she posted this cover (pp. 139-140).  She writes:

Towards the end of October, 1916, Marie Adelaide left her Duchy for the first time since the outbreak of the war.  It was to go to Königstein, near Frankfurt, the estate that years before the Grand Duke Adolf had given to his consort, Adelheid Marie of the House of Anhalt.  There she stood by the bedside of that mortally-stricken, beloved figure of her childhood, of her adolescence, of her reign.  Again on November 20th, she went to bury her.

Adelheid-Marie, seen in the images below, was born in Dessau on December 25, 1833, and died at Schloss Königstein on November 24, 1916.  Sadly, Marie-Adélaïde's visits to her dying grandmother were used by her political opponents as evidence that she had been sympathetic to Germany during World War I.