What is the ruling regarding a woman who says that she will not adhere to the Prophet's—peace and blessings be upon him—directives concerning adornment and Islamic dress, even if he were to directly command her, because she cannot abandon fashion and the joys of youth?

Sins are not disbelief (kufr) but rather disobedience (fisq), even if they are major sins, unless they are coupled with deeming them permissible (istihlāl) or treating lightly the One who forbade them, which contradicts faith. Thus, whoever treats lightly the status of the Messenger (peace be upon him) and prefers this world over the Hereafter, there is a fear of deviance for him. Sheikh al-Islam Ibn Taymiyyah clarified that disobeying the command of the Messenger (peace be upon him) can lead to disbelief if it is coupled with treating it lightly, similar to the action of Iblis. This differs from the case of one who commits a sin due to a whim of the soul while disliking it and revering the law of Allah; such a person does not exit the fold of Islam.