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 is His slave and Messenger.
What should be taken into account is the state of that woman now. If she is Christian, then it is permissible for a Muslim to marry her provided that she is chaste. Please refer to fatwa 82067.
However, some scholars are of the view that it is disliked to marry a woman from the People of the Book, regardless of whether she is Jewish or Christian – even if she is chaste – because of some Islamic prohibitions. Please refer to fatwa 84159 in this regard.
It is better and more appropriate for a Muslim to marry a pious Muslim woman, as it is hoped that he will live with her in happiness and that she will help him in raising his children on the beliefs and morals of Islam. This is because they both have the same religion and both strive to please Allaah, the Lord of the Worlds.
Allaah knows best.