Her husband, four years younger than she was, was not only under the legal control of his aunt and guardian, the "magnificent" and proud Mademoiselle de Guise (Marie de Lorraine de Guise), but in day-to-day protocol, he was treated by Isabelle as the social inferior that he was.
Soțul ei, care era cu patru ani mai tânăr decât ea, nu era numai sub controlul legal al mătușii sale, Mademoiselle de Guise (Marie de Lorena de Guise), dar în protocolul obișnuit el era tratat ca inferior Isabelei.