It should be clear, first of all, that betrothal, literally, customarily and legally, is different from marriage. It is an introduction and a promise to marry. it is permissible for engaged couples to talk to each other on telephone occasionally and they may write to each other, but the content of their conversation must be halal.
Dr. Muzzamil Siddiqi, former president of the Islamic Society of North America (ISNA), states the following: “The Prophet, peace and blessings be upon him, not only permitted but encouraged the young people to see their prospective spouses before engagement. Jabir, may Allah be pleased with him, quoted the Prophet, peace and blessings be upon him, as saying: “When one of you make a proposal of marriage to a woman, if you can see what can invite you to marry her then do so.”
When Mughirah Ibn Shu’bah, may Allah be pleased with him, made a proposal of marriage to woman, the Prophet, peace and blessings be upon him, asked him, “Have you seen her?” He said, “No.” The Prophet said to him, “See her, because this may make your relationship more permanent.” (Reported by An-Nasa’i, Ibn Majah and At-Timidhi)
On the basis of these and other similar Hadiths, the jurists have said that it is allowed for a boy and girl who are considering to marry each other to see and meet each other in the presence of their adult relatives. The meetings should be supervised and with proper Islamic dress and etiquette.
they are not allowed to go out alone or to spend time together alone. Even after the engagement or khitbah they should not have any unsupervised meetings.
They may talk to each other on telephone occasionally or they may write to each other, but they should observe modesty in their conversations and must always remember that they are still unmarried and whatever is allowed for married couples is not yet allowed to them.
In the past, some Muslims used to take an extreme position in this matter. They would not allow their boys and girls to see their prospective spouses at all. The first time they would see and meet each other would be on the night of their union. This was just a cultural practice and not an Islamic custom.
now, the trend has gone to another extreme un-Islamic practice. It is observed in many Muslim, even in some religious, families that boys and girls are allowed to meet freely and go out without any supervision. This is unlawful and it must be stopped. Such practices, if continued, will corrupt Muslim families and weaken our family structure just as it happened to many non-Muslim families.”
Having clarified the above, it becomes clear that in this period it is not permissible for Muslim couples to exchange words of love. However, one may tell his fiancée that he is admired of her good morals and character. It is allowed to use written methods of communication as long as they abide by the ethics and morals of Islam regarding talking between people of the opposite sex.