How to treat a Muslim girl who has married a Non- Muslim?
A muslim girl marries a non-Muslim. What should her parents do? What should be the right attitude? What about their treatment towards the daughter? Should the parents not convey their displeasure and break contact with her?
The parents should have tried their best to convince their daughter that she shouldn't get married to the man. However, once the marriage takes place, they should make her husband a part of the family, treat him well, and pray to God that he becomes a Muslim. They have no obligation except da'wah towards the couple. The daughter should be made to realise that the best hope she has from God's mercy is that her husband becomes a Muslim. She should pray for it and behave well with him so that he is attracted towards Islam.
There are two possible approaches for the parents to follow: Abandon the daughter and lose her for ever or create an attitude of da'wah which could convert a wrong act into a right one. In the latter way, there is some hope. The parents should be thankful that their daughter didn't become a non-Muslim. Even in that case I wouldn't have advised them to sever their contacts with her.
I am giving the above advice because although it seems likely on the balance that a Muslim lady cannot marry a non-Muslim man, there is no clear verdict to that effect. We will therefore neither declare such a marriage haram nor halal. The important principle is that neither of the spouses should indulge in shirk (polytheism).
And Allah knows the best.