Is it permissible to marry a married Christian woman an 'urfi (customary) marriage, knowing she wishes to convert to Islam but fears her family and her estranged husband's family?

It is not permissible to marry a married woman unless she is divorced or the marriage contract is annulled. The contract is annulled if the woman embraces Islam while her husband is a disbeliever and he does not embrace Islam during her iddah (waiting period). If the husband is a Muslim, then it is not possible to marry her unless she is divorced or she resorts to a judge to remove the harm if the husband is absent. The woman should be encouraged to embrace Islam by explaining its virtues, and this task should be undertaken by a woman. To avoid threats, she can resort to the authorities and conceal herself from her family.