She has embraced Islam but her husband is still a kaafir. What should she do?
Question

                What is the ruling about remaining in a
      marriage when the wife has become a Muslim but her husband is still a kaafir? She has
      children with him and is afraid that they may go astray and be lost, and she hopes that
      her husband may be guided to Islam if she stays with him.
Praise be to Allah.As soon as a woman embraces Islam and her husband refuses to do
    likewise, the marriage is annulled and it is not permissible for her to live with him. But
    she should wait out the length of the ‘iddah period. If he embraces Islam, she may go
    back to him and the previous marriage contract is still counted as valid, but if he does
    not embrace Islam before the ‘iddah is over, then they are no longer married. If he
    subsequently embraces Islam and they want to get back together, a new marriage contract
    must be drawn up. It is not permissible to continue the marriage on the basis of being
    kind to him.
Majma’ al-Fiqh al-Islami (Islamic Fiqh Council), p. 43.
The children should follow the Muslim parent, so try
    your best to get custody of them. May Allaah help us and help you by His kindness and
    mercy.