It is not permissible for a Muslim man to marry a woman who is a Mushrik. Christians and
are not included in this ruling. One is not permitted to marry a disbelieving woman even if she agrees to do so, and whether or not the person has told her that he is a Muslim. Allah (Exalted be He) says:
And do not marry Al-Mushrikât (idolatresses, etc.) till they believe (worship Allâh Alone).
If she repents from her Shirk (associating others with Allah in His Divinity or worship) and embraces Islam, he will be permitted to marry her. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.