Is the marriage of a Christian woman, married to a Christian man, rendered null and void should she embrace Islam and desire to marry a Muslim man?

Love is not permissible in Islam except between spouses. It is also not permissible to incite a woman against her husband. A non-belligerent disbeliever has a sanctity that prohibits aggression against his wealth and honor. If a woman embraces Islam, it is not permissible for her to remain with her disbelieving husband, due to the Almighty's saying: "Then if you ascertain that they are believers, do not return them to the disbelievers; neither are they lawful for them, nor are they lawful for them," and the Almighty's saying: "And never will Allah grant the disbelievers a way over the believers." If her husband embraces Islam before the expiry of her iddah (waiting period), then he has more right to her. Otherwise, you may marry her, like other Muslims, after she completes her iddah.