What are the consequences of a wife accusing her husband of disbelief (kufr) and seeking divorce based on that, and what is the ruling on a wife seeking khul' in this situation?

Accusing a Muslim of disbelief (kufr) is a grave sin (kabira), as the Prophet, peace and blessings be upon him, said: "If a man calls his brother 'O disbeliever,' then it has returned upon one of them." And he said: "Whoever calls a man a disbeliever or says 'O enemy of Allah,' and he is not so, then it redounds upon him." Issuing a ruling of disbelief (takfir) is a judicial matter pronounced by those qualified. Deal with your wife wisely and seek advice and reconciliation from her family's people of sound judgment. If that proves difficult, divorce by mutual consent (khul') is permissible, as the Prophet, peace and blessings be upon him, commanded it when necessary, as in the story of the wife of Thabit ibn Qays, who disliked disbelief in Islam. Refer the matter to the Sharia court for consideration.