All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ʻalayhi wa sallam, is His slave and Messenger.
If the woman's husband did not issue a divorce or accept the khul’, then she is still his wife as per the sharee'ah and the divorce decree issued by the non-Muslim judge is worthless; divorce does not take effect in this case. Please, refer to fatwa 287599.
There is no doubt that her marriage to another man is invalid and that their relationship must be terminated immediately. If she wants to have a legitimate divorce or Khul’, then she should refer the case to the Islamic centers. The statement issued by the Assembly of Muslim Jurists of America (AMJA) reads:
“The seventh point: To what extent the civil divorce in courts outside Muslim countries can be relied upon:
The decision clarified that if a man divorces his wife Islamically, then it is permissible to authenticate it in non-Islamic courts. However, if there is a dispute about divorce between the spouses, then the Islamic Centers act on behalf of the Islamic courts if the latter are not existent, after completing the necessary legal procedures. Resorting to non-Islamic courts in order to terminate the marriage in a legal manner does not lead by itself to the termination of the marriage Islamically. If a woman obtains a divorce from a civil court, then she should refer the case to Islamic Centers to be further investigated by the competent scholars in these issues in order to finalize the matter Islamically. Needless to assert that there is no necessity to resort to civil courts in case there are Islamic Centers since they are available and easy to resort to in the various parts of the world.”
Allaah knows best.