What should the wife do if her husband claims her desire for divorce is due to her thinking of another man and her sexual coldness towards him, despite her love for him and her denial of his claims, and they have seven children?

This action by the husband is wrong, and he has no right to accuse his wife without evidence. The wife must make clear to her husband her innocence and purity, and affirm to him her love and desire for the marriage to continue, even if it necessitates taking an oath. She should strive to change the image of her unwillingness to engage in intercourse that planted doubt in his mind, by drawing closer to him and showing affection. It is also advised to turn to Allah Almighty, and seek help from the husband's or wife's family if possible, and to review one's worship and obedience, and to increase in prayer, remembrance of Allah (dhikr), and recitation of the Quran, especially Surah Al-Baqarah.