She was only twelve years old and engaged to Hugh de Lusignan when King John of England became infatuated with her. Preferring her to be Queen of England, her parents had the engagement annulled and allowed her to marry King John.
Seven years later she gave birth to their first child, the future King Henry III, soon to be followed by two more children. However, John was an unfaithful husband and Isabella's flirtations caused
disharmony between them. In 1212 John had Isabella locked up at Gloucester but a year later they became reconciled and two more children were born.
When John died in 1216 Isabella was at Gloucester with her children and she immediately proclaimed their eldest son to be King Henry III. For safety against the French invaders she sent her younger son Richard to Ireland. In July 1217 she returned to France where she met her old fiancee, Hugh de Lusignan, who was by now engaged to Isabella's daughter Joan. However, as Joan was only ten years old and Hugh needed an heir soon, he married Isabella instead and they became the parents of five sons and at least three daughters.
Henry III had not been consulted about his mother's remarriage and, even though he was only thirteen-years-old, he deprived his mother of her dowry. It took a year before a reconciliation took
place.
In 1242 Hugh and Isabella were accused of plotting against the life of King Louis IX of France. Isabella attended the court but remained seated on her horse and, when she realised the hearing would go against her, she rode off to take refuge in the Abbey of Fontevraud where she remained the rest of her life. Although Hugh de Lusignan was able to placate the French king, Isabella remained at Fontevraud where she died and was buried. Hugh de Lusignan then went on crusade and was killed while fighting in 1249.
 

Source: Leo van de Pas