According to Douglas Richardson: "There is a charter which proves that Countess Isabel survived her 2nd husband, William de Warenne, 2nd Earl of Surrey. This charter was published in Salzman, ed., The Chartulary of the Priory of St. Pancras of Lewes, Part 1 (Sussex Record Society 38) (1932): 29. This charter is dated c.1138 and was issued by Countess Isabel and her son, William de Warenne, 3rd Earl of Surrey." Charles Cawley says "The necrology of Saint-Nicaise de Meulan records the death "XIII Kal Mar" of "Isabel comitissa Mellenti". There appears to be no other "Isabelle Ctss de Melun" to whom this can refer apart from Isabelle de Vermandois. However, it is surprising that she is not referred to by the title of her second husband."

According to Douglas Richardson: "There is a charter which proves that Countess Isabel survived her 2nd husband, William de Warenne, 2nd Earl of Surrey. This charter was published in Salzman, ed., The Chartulary of the Priory of St. Pancras of Lewes, Part 1 (Sussex Record Society 38) (1932): 29. This charter is dated c.1138 and was issued by Countess Isabel and her son, William de Warenne, 3rd Earl of Surrey." Charles Cawley says "The necrology of Saint-Nicaise de Meulan records the death "XIII Kal Mar" of "Isabel comitissa Mellenti". There appears to be no other "Isabelle Ctss de Melun" to whom this can refer apart from Isabelle de Vermandois. However, it is surprising that she is not referred to by the title of her second husband."