What is the ruling on a sister exceeding the limits in conversation with her fiancé via phone and internet, while she refuses to عقد النكاح (consummate the marriage contract) and her family interferes?

The suitor remains a stranger to his fiancée until the legal marriage contract is concluded. The sister jesting with her suitor is a reprehensible act and an open door to temptation. The questioner has done well in advising her sister and should continue to do so gently and kindly, reminding her that this disobedience may hinder the completion of the marriage or diminish its blessings, as Allah Almighty says: "And whatever strikes you of disaster - it is because of what your hands have earned; and He pardons much." If the sister does not repent, the questioner should inform her guardian, who must prevent her from doing so, as he is responsible for her before Allah, as Allah Almighty says: "O you who have believed, protect yourselves and your families from a Fire whose fuel is people and stones." Much supplication should be made for her rectification and guidance, and the marriage should be promptly concluded to resolve the issue.