Will her ex-husband be held accountable on the Day of Judgment for her betrayal of him, by taking her good deeds and casting his bad deeds upon her? And what advice do you offer her?

A woman who has committed a forbidden act must repent to Allah by abandoning the sin, regretting it, and resolving never to return to it. She must also seek forgiveness from her husband and ask for his absolution, unless she fears a greater harm. In such a case, she should seek general absolution without specifying the sin, because she has defiled his honor and fallen short in her duty to him. It has been narrated in a Hadith (definition) that a husband has the right over his wife that no one he dislikes should tread upon their فرش (beds/homes), which includes not permitting anyone to enter the marital home except those whom the husband approves. If she does not seek absolution from her husband, she will be exposed to retribution through good deeds and bad deeds. However, some scholars hold that if, in such matters, seeking absolution is likely to result in greater harm, then supplicating for the rights-holders is sufficient, and seeking absolution is not obligatory.