Question: Who was the granddaughter of Queen Victoria of the United Kingdom who also has a grandson that was the first descendant of all three of Victoria, Duchess of Kent's children?
Context: Emich was born at Coburg, Weimar Republic, the first child of Karl, Prince of Leiningen (1898–1946), (son of Emich, 5th Prince of Leiningen and Princess Feodore of Hohenlohe-Langenburg) and his wife, Grand Duchess Maria Kirillovna of Russia (1907–1951), (daughter of Cyril Vladimirovich, Grand Duke of Russia and Princess Victoria Melita of Saxe-Coburg and Gotha).  Through his mother, he was a descendant of Queen Victoria and Tsar Alexander II.  Through his father, he was a descendant of the Vasa kings of Sweden and of both of Queen Victoria's half-siblings, Carl, Prince of Leiningen and The Princess of Hohenlohe-Langenburg.  As a result, Emich was the first descendant of all three of Victoria, Duchess of Kent's children. Princess Henriëtte van Nassau-Weilburg, then van Nassau (22 April 1780, in Kirchheimbolanden – 2 January 1857, in Kirchheim unter Teck) was a daughter of Prince Charles Christian, Duke of Nassau-Weilburg and Carolina of Orange-Nassau, daughter of William IV, Prince of Orange.  Queen Elizabeth II of the United Kingdom is her descendant through Francis, Duke of Teck, Henriette's grandson.  Prince Philip, Duke of Edinburgh is her descendant through her granddaughter Princess Alexandra of Saxe-Altenburg, who is the grandmother of Prince Andrew of Greece and Denmark.  Juan Carlos I of Spain is a descendant of her granddaughter Archduchess Elisabeth Franziska of Austria, the grandmother of Alfonso XIII of Spain. Princess Alexandra of Saxe-Coburg and Gotha, , (Alexandra Louise Olga Victoria; 1 September 1878 – 16 April 1942), was the fourth child and third daughter of Alfred, Duke of Edinburgh and Grand Duchess Maria Alexandrovna of Russia.  She was a granddaughter of Queen Victoria of the United Kingdom as well as of Tsar Alexander II of Russia. The Kensington System was a strict and elaborate set of rules designed by Victoria, Duchess of Kent, along with her attendant, Sir John Conroy, concerning the upbringing of the Duchess's daughter, the future Queen Victoria.  It is named after Kensington Palace in London, where Victoria resided with her mother prior to acceding the throne. Princess Alice, Countess of Athlone, (Alice Mary Victoria Augusta Pauline; née Princess Alice of Albany; 25 February 1883 – 3 January 1981) was a member of the British Royal Family.  She is the longest-lived Princess of the Blood Royal of the British Royal Family, and was the last surviving grandchild of Queen Victoria.  She also held the titles of Princess of Saxe-Coburg and Gotha and Duchess in Saxony from birth, as well as a Princess of Teck by marriage, until 1917 when the British Royal Family ceased usage of German titles.  She was godmother to Queen Beatrix of the Netherlands, who is the granddaughter of her first cousin on her mother's side, Queen Wilhelmina of the Netherlands. Princess Alice of the United Kingdom, (Alice Maud Mary; 25 April 1843 – 14 December 1878; later Princess Louis of Hesse and Grand Duchess of Hesse and by Rhine) was the third child and second daughter of Queen Victoria and Albert, Prince Consort.  Alice was the first of Queen Victoria's nine children to die, and one of three to be outlived by their mother, who died in 1901. Karl Vladimir Ernst Heinrich, Prince of Leiningen (2 January 1928 – 28 September 1990) was the son of Karl, 6th Prince of Leiningen (1898–1946) and Maria Kirillovna of Russia.  Maria was the daughter of Princess Victoria Melita of Edinburgh and Saxe-Coburg-Gotha, a paternal granddaughter of Queen Victoria of the United Kingdom, and Cyril Vladimirovich, Grand Duke of Russia.  As such, Karl was a great-great-grandson of Queen Victoria and Alexander II of Russia (as Victoria Melita and Cyril Vladimirovich were both grandchildren of Alexander II). Princess Victoria Melita of Saxe-Coburg and Gotha and Edinburgh , later Grand Duchess Victoria Feodorovna of Russia (25 November 1876 – 2 March 1936) was the third child and second daughter of Alfred, Duke of Saxe-Coburg and Gotha, and Grand Duchess Maria Alexandrovna of Russia.  She was a granddaughter of Queen Victoria of the United Kingdom and Emperor Alexander II of Russia. Donatus, Prince and Landgrave of Hesse ("Heinrich Donatus Philipp Umberto"; born 17 October 1966) is the eldest son and successor of German aristocrat Moritz, Landgrave of Hesse, and his former wife, Princess Tatiana of Sayn-Wittgenstein-Berleburg.  A great-grandson of Victor Emmanuel III of Italy, he is named in part after Georg Donatus, Hereditary Grand Duke of Hesse.  He is also a great-great-great grandson of Queen Victoria of the United Kingdom, through his paternal grandfather Philipp's mother Margaret, a granddaughter of Queen Victoria.  His father Moritz was a third cousin of Queen Elizabeth II of the United Kingdom. Princess Arthur of Connaught, 2nd Duchess of Fife, GCStJ (Alexandra Victoria Alberta Edwina Louise; née Duff; "Princess Alexandra, Duchess of Fife" before marriage; 17 May 1891 – 26 February 1959) was a granddaughter of King Edward VII and great-granddaughter of Queen Victoria.
Answer: Princess Victoria Melita of Saxe-Coburg and Gotha