Question: When Violet Wegner became HRH Princess Pierre of Montenegro, who was her sister-in-law?

full_context: Document 1: Violet Manners, Duchess of Rutland: Marion Margaret Violet Manners, Duchess of Rutland ("née" Lindsay; 7 March 1856 – 22 December 1937) was a British artist and noblewoman. A granddaughter of the 24th Earl of Crawford, she married Henry Manners in 1882. She was styled as the Marchioness of Granby from 1888 to 1906, when Manners succeeded as Duke of Rutland. She had five children, including the 9th Duke of Rutland and the socialite Lady Diana Cooper.
Document 2: Princess Stéphanie of Belgium: Princess Stéphanie of Belgium (21 May 1864 – 23 August 1945) was a Belgian princess by birth and became Crown Princess of Austria through her marriage to the heir-apparent of the Habsburg dynasty, Archduke Rudolf. She was famously widowed in 1889 when Rudolf and his mistress, Mary Vetsera, were found dead in an apparent murder-suicide pact at the Imperial hunting lodge at Mayerling in the Vienna Woods.
Document 3: Violet Melnotte: Violet Melnotte (2 May 1855–17 September 1935), was a stage performer and actress-manager and theatre owner of the late 19th century and early 20th century. She was the wife of Gilbert and Sullivan performer Frank Wyatt, whom she met when they both appeared in the hit operetta "Erminie".
Document 4: Elvina Pallavicini: Princess (Italian: "principessa" ) Elvina Pallavicini (22 January 1914 - 29 August 2004) was an Italian noblewoman, member of the Pallavicini family, part of, and often considered the leader of, the so-called Black Nobility in Rome during the second half of the 20th century.
Document 5: Elena of Montenegro: Princess Elena of Montenegro or more commonly known as Queen Elena of Italy (8 January 1871 – 28 November 1952) nicknamed "Jela" was the daughter of King Nicholas I of Montenegro and his wife, Milena Vukotić. As wife of Victor Emmanuel III of Italy, she was Queen of Italy from 1900 until 1946 and Queen consort of the Albanians from 1939 until 1943.
Document 6: Prince Nikola of Yugoslavia (born 1958): Prince Nikolas of Yugoslavia (born 15 March 1958) is a member of the House of Karadordevic. Currently fourth in the line of succession to the defunct Yugoslavian throne, he is also in the line of succession to the British throne as a great-grandson of Princess Marie of Edinburgh, herself a granddaughter of Victoria of the United Kingdom.
Document 7: Albanian Kingdom (1939–43): The Albanian Kingdom (Gheg Albanian: "Mbretnija Shqiptare", Standard Albanian: "Mbretëria Shqiptare", Italian: "Regno albanese" ), also known as Greater Albania, existed as a protectorate of the Kingdom of Italy. It was practically a union between Italy and Albania, officially led by Italy's King Victor Emmanuel III and its government: Albania was led by Italian governors, after being militarily occupied by Italy, from 1939 until 1943. During this time, Albania ceased to exist as an independent country and remained as an autonomous part of the Italian Empire led by Italian government officials, who intended to make Albania part of a Greater Italy by assimilating Albanians as Italians and colonizing Albania with Italian settlers from the Italian Peninsula to transform it gradually into an Italian land.
Document 8: Baroness Mary Vetsera: Baroness Marie Alexandrine von Vetsera (19 March 1871 – 30 January 1889) was a member of Austrian "second society" (new nobility) and one of Crown Prince Rudolf of Austria's mistresses. Vetsera and Rudolf were found dead, an apparent murder suicide, at his hunting lodge, Mayerling (see Mayerling Incident).
Document 9: Grand Duchess Elena Vladimirovna of Russia: Grand Duchess Elena Vladimirovna of Russia (17 January 1882 – 13 March 1957), sometimes known as Helen, Helena, Helene, Ellen, Yelena, Hélène, or Eleni, was a Russian grand duchess as the only daughter and youngest child of Grand Duke Vladimir Alexandrovich of Russia and Duchess Marie of Mecklenburg-Schwerin. Her husband was Prince Nicholas of Greece and Denmark and they were both first cousins of Tsar Nicholas II of Russia.
Document 10: Alma Vetsera Hayne: Alma Vetsera Hayne (1890–1919) was a New York City socialite who passed herself off as the daughter of Rudolf, Crown Prince of Austria and Baroness Mary Vetsera and called herself Princess Vetsera of Austria. She claimed her son, Rudolph Hayne (1899-?), was heir to the Austro-Hungarian throne.
Document 11: Umberto I of Italy: Umberto I (Italian: "Umberto Ranieri Carlo Emanuele Giovanni Maria Ferdinando Eugenio di Savoia" ; 14 March 1844 – 29 July 1900), nicknamed "the Good" (Italian: "il Buono"), was the King of Italy from 9 January 1878 until his assassination on 29 July 1900.
Document 12: Princess Maria Pia of Bourbon-Parma: Princess Maria Pia of Bourbon-Parma (née Princess Maria Pia of Savoy; born 24 September 1934) is the eldest daughter of Umberto II of Italy and Marie-José of Belgium. She is the older sister of Princess Maria Gabriella of Savoy, Vittorio Emanuele, Prince of Naples, and Princess Maria Beatrice of Savoy.
Document 13: Violet Wegner: Violet Emily Wegner, (1887-1960), was the daughter of an Extradition Department detective of Scotland Yard, William T. Wegner, and Arabella Eliza née Darby, who resided in a district of London called Tulse Hill. Violet made a career in the music halls from the age of 15. She became known as the "Idol of Berlin". In 1912, Violet married her first husband, Sergio Francesco Enrico Maria Brunetta d'Usseaux (born 3 March 1885, Torino, Italy), in London. Sergio's parents were Comte Eugenio Brunetta d'Usseaux and the Russian Countess Zeiffart. Eugenio was Secretary General of the Olympic Committee that administered the 1908 London Olympics. Eugenio died in 1919 in mysterious circumstances. The fate of his son, and Violet's husband, is also unknown although it is suggested he may have been the son Eugenio was trying to reach following the October Revolution. Whilst traveling in Italy during 1918, Violet met the youngest son and royal prince, Pierre Petrović-Njegoš, of the exiled King Nicholas I of Montenegro. After some delay, it is said, at the behest of Violet's mother who advised them to await the award of monies claimed by the prince from the new Yugoslav government for the confiscation of his family's property in Montenegro, Violet married Prince Pierre (Peter) of Montenegro in Paris in the April of 1924. Violet then became HRH Princess Pierre of Montenegro and thus sister-in-law to Queen Elena of Italy as well as a host of other European princes and kings via her husband's siblings.
Document 14: Susan of Albania: Susan, Crown Princess of Albania ("née" Cullen-Ward, formerly Williams; 28 January 1941 – 17 July 2004), also known as Susan Barbara Zogu and Queen Susan of the Albanians (Albanian: "Suzana Zog, Mbretëreshë e Shqiptarëve"), was the Australian-born wife of Leka, Crown Prince of Albania.
Document 15: Georgina Worsley (Upstairs, Downstairs character): Georgina Worsley arrives to live at Eaton Place in 1913. She is the step-daughter of Lady Marjorie's brother Hugo Talbot-Carey (the new Earl of Southwold). His new wife is the widow Marion Worsely, and mother of Georgina by her previous marriage. Georgina's natural father died in a hunting accident when she was six years old. Her mother and step-father die along with Lady Marjorie in the sinking of the "RMS Titanic" in 1912. After that she moves into 165 Eaton Place right before Christmas in December 1913.
ground_truth: Elena of Montenegro