Question: Who is the wife of Charlemagne who is a step mother to Pepin the Hunchback?

Context paragraphs:
Koji Ota: Koji Ota (太田 幸司 , Ōta Kōji , born January 23, 1952 in Misawa, Aomori, Japan) is a Japanese former professional baseball pitcher in Japan's Nippon Professional Baseball, and belongs to Mainichi Broadcasting System, Inc. as a commentator in baseball live on radio and TV.  Ota is a son of an American father and a Japanese mother, the adopted son of a Japanese step father and a Russian step mother, who emigrated to Japan because of the Russian Revolution in 1917.

Charlemagne, le prince à cheval: Charlemagne, le prince à cheval is a 1993 television miniseries about the life of Charlemagne.  It consists of five episodes and covers the period from the death of his father, Pepin the Short in AD 768 until Charlemagne's corronation as the first Holy Roman Emperor on Christmas Day, AD 800.  However, there is a minor chronological anachronism: in an earlier episode, we see Widukind, the king of the Saxons surrender and convert to Christianity, which didn't happen until AD 803.

Pepin of Italy: Pepin or Pippin (or "Pepin Carloman", "Pepinno", April 773 – 8 July 810), born Carloman, was the son of Charlemagne and King of the Lombards (781–810) under the authority of his father.

Godescalc Evangelistary: The Godescalc Evangelistary, Godescalc Sacramentary, Godescalc Gospels, or Godescalc Gospel Lectionary (Paris, BNF.  lat.1203) is an illuminated manuscript made by the Frankish scribe Godescalc and today kept in the Bibliothèque nationale de France.  It was commissioned by the Carolingian king Charlemagne and his wife Hildegard on October 7, 781 and completed on April 30, 783.  The Evangelistary is the earliest known manuscript produced at the scriptorium in Charlemagne's Court School in Aachen.  The manuscript was intended to commemorate Charlemagne's march to Italy, his meeting with Pope Adrian I, and the baptism of his son Pepin.  The crediting of the work to Godescalc and the details of Charlemagne's march are contained in the manuscript's dedication poem.

Lambert III of Nantes: Lambert III was born in 830 and died in 882.  Lambert was the son of Lambert II of Nantes, at whose death in 851, the administration of the region fell effectively to the Bretons.  After his father's death, Lambert III became a pretender to the County of Nantes seat.  His mother was Tetrata of Lombardy, a daughter of the eldest son of Charlemagne, Pepin of Italy.  Lambert III married Rotrude of Italy, a daughter of Holy Roman Emperor Lothair I.  The Emperor was a first cousin of Lambert's mother, as both were grandchildren of Charlemagne.  Lambert's and Rotrude's only son was Wipert of Nantes.

Fulrad: Saint Fulrad (French: "Fulrade" ; Latin: "Fulradus" ) was born in 710 into a wealthy family, and died on July 16, 784 as the Abbot of St. Denis.  He was the counselor of both Pippin and Charlemagne.  Historians see Fulrad as important due to his significance in the rise of the Frankish Kingdom, and the insight he gives into early Carolingian society.  He was noted to have been always on the side on Charlemagne, especially during the attack from the Saxons on Regnum Franserum (Latin for Frankia), and the Royal Mandatum (a royal official of the Carolingian administrative hierarchy).  Other historians have taken a closer look at Fulrad’s interactions with the papacy.  When Fulrad was the counselor of Pepin he was closely in contact with the papacy to gain approval for Pepin’s appoint as King of the Franks.  During his time under Charlemagne, he had dealings with the papacy again for different reasons.  When he became Abbot of St. Denis (N.E of Paris), Fulrad’s life became important in the lives of distinct historical figures in various ways during his period as St. Denis’s abbot during the mid-eighth century.  Saint Fulrad’s Feast Day is on July 16.

Hildegard of the Vinzgau: Hildegard (ca. 754 – 30 April 783 at Thionville, Moselle), was the second wife of Charlemagne and mother of Louis the Pious.  Little is known about her life, because, like all women of Charlemagne, she became important only from a political background, recording her parentage, wedding, death and her role as a mother.

Carloman I: Carloman I, also "Karlmann" (28 June 751 – 4 December 771) was king of the Franks from 768 until his death in 771.  He was the second surviving son of Pepin the Short and Bertrada of Laon and was a younger brother of Charlemagne.  No one knows who killed him.  Carloman is mainly regarded by historians as Charlemagne's first steps towards acquiring the Holy Roman Empire, as his death allowed Charlemagne to take all of Francia and begin his expansion into other kingdoms.

Charles the Younger: Charles the Younger of Charles of Ingelheim (c. 772 – 4 December 811) was a member of the Carolingian dynasty, the second son of Charlemagne and the first by his second wife, Hildegard of Swabia and brother of Louis the Pious and Pepin Carloman.  When Charlemagne divided his empire among his sons, his son Charles was designated King of the Franks.

Pepin the Hunchback: Pepin, or Pippin, the Hunchback (French: Pépin le Bossu, German: Pippin der Buckelige; c. 769 – 811) was the eldest son of Charlemagne.  Born to the Frankish noblewoman Himiltrude, Pepin probably developed kyphosis after birth, leading early medieval historians to give him the epithet "hunchback".  He lived with his father's court even after Charlemagne dismissed his mother and took another wife, Hildegard.  Around 781, Pepin's half brother Carloman was rechristened as "Pepin of Italy"—a step that may have signaled Charlemagne's decision to disinherit the elder Pepin, for a variety of possible reasons.  In 792, Pepin the Hunchback revolted against his father with a group of leading Frankish nobles, but the plot was discovered and put down before the conspiracy could put it into action.  Charlemagne commuted Pepin's death sentence, having him tonsured and exiled to the monastery of Prüm instead.  Since his death in 811, Pepin has been the subject of numerous works of historical fiction.

Supporting paragraphs: Pepin the Hunchback Hildegard of the Vinzgau
Answer: Hildegard