Leonor!
Or how a woman changed history completely.
Aenor and William of Aquitaine's daughter Elionor(Alienor) or Leonor was betrothed to the King of France, Louis VII, Leonor was the only successor of Aquitaine.
Leonor was very happy to be with King Louis VII and had two daughters, Marie of Champagne and Alice of Blois and Leonor even joins crusades and wins battles there.
Leonor's marriage with Louis VII was annuled because of consanquinity later on and Sancho of Castile broke his engagement to Blanca of Navarre then Leonor married Sancho II of Castille in 1153 after her unpopular marriage with Louis VII and had seven children with him, Ricardo, Juan, Sancho VII, Felipe, Constanza, Isabel and Leonor
Leonor made her children rebel against Sancho and made his army weak causing a loss of a part of Castille to the moors later on Ricardo becomes the King of Castille and the Duke of Aquitaine.