How should I deal with my daughter who considers herself engaged to someone not of her religion, and with this person, and should I cut ties with them if they get married?

The approach to dealing with a daughter involved in an illicit relationship is as follows: Firstly, remind her of God and the Last Day, and explain the grave danger of her action, clarifying that it is explicit and impermissible fornication. Secondly, threaten and warn her verbally if she does not respond. Thirdly, forcibly prevent her from meeting this person or marrying him if words prove ineffective. Fourthly, if you are unable to do so, then you must emigrate from this country with your daughter to an Islamic country.