What is the religious ruling regarding a wife who swears by disavowing Islam?

What the wife did is a heinous sin, and she must hasten to repent and seek forgiveness. Scholars differed regarding the validity of an oath made by saying "حرام عليّ" (it is forbidden for me): some of them believe it is an oath that requires an expiation for breaking it, while the majority of scholars believe that it is not a valid oath, so no expiation is due if she does the sworn-upon act. She is not considered to have disbelieved unless she harbored disbelief in her heart.