Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
If it had become clear to a woman that her husband had committed Zina (adultery), then she must advise him and warn him against the punishment that Allah has prepared for a fornicator and adulterer in this life and in the Hereafter. If he accepts the admonition and repents Al-Hamdu Lillah (Praise be to Allah), Allah accepts the repentance of His slaves and forgives the sins, but if he does not listen and continues to commit adultery, then it is desirable for her not to stay with him and she can ask for divorce. If the suitability in marriage becomes void during the contract then it can be invalidated according to one of the two opinions of the scholars.
But we said that it is not an obligation on her to ask for a divorce because he committed adultery.