She married Robert de Vere, 3rd Earl of Oxford, and was a benefactress of the Order of Friars Preacher (Dominicans) in England.

Oxford made peace with the regents of John's son, Henry III the next year, and later served as a royal judge.

[8] On the death of Earl Robert, the widowed Countess purchased the wardship of her minor son from the crown for the substantial sum of 6000 marks.

[10] Isabel was a benefactress of the Order of Friars Preacher (Dominicans) in England,[11] helping them to find quarters at Oxford, and contributing to the building of their oratory there about 1227.

When the friars needed a larger priory, she and the Bishop of Carlisle bought land south of Oxford and contributed most of the funds and materials.