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.
It is Islamically permissible in principle to marry a woman from the people of the Book provided she is chaste; for more benefit in this regard, please refer to Fatwa 82067.
However, you are wrong in saying that burying baby-girls alive was the reason why Allaah permitted marrying the women from the people of the Book. Indeed, Allaah mentioned this ruling, which is the permissibility of marrying the women from the people of the Book in chapter 5, the verses of which were the last verses to be revealed from the Quran at a time when the Muslims became firm in their belief and the practice of burying baby-girls alive was abolished. However, the scholars disliked marrying the women from the people of the Book due to the disadvantages which may happen. For more benefit in this regard, please refer to Fataawa 89418 and 84724.
As regards the marriage of a Muslim woman to a non-Muslim man, then it is an invalid marriage; for more benefit, please refer to Fatwa 83101. If what you mentioned is correct that some Muslim women married non-Muslim men, then this is very grave, and the one who stays in this condition is a fornicator. The fact that no Muslim man married them is not a reason for them to marry non-Muslims. Their guardians and the people who are running the affairs of Muslims there should endeavour to solve this problem as it is very grave for them to stay with their non-Muslim husbands.
Every effort should be made so that Muslim women marry Muslim men in order that this matter will not be repeated.
Allaah Knows best.