What is the ruling on congratulating a Christian fiancée on her holidays, and is that considered showing loyalty to disbelievers?

It is not permissible for a Muslim to participate with the People of the Book in their holidays by offering gifts or congratulations, because that is part of the rituals of their false religion, and we have been forbidden from agreeing with them in their holidays. It is also necessary to be cautious about showing complaisance in this matter, as it may lead to loyalty towards polytheists. If the fiancée is from the People of the Book, she must be invited to Islam and shown the virtues of Islamic law. However, if she is merely a fiancée (not from the People of the Book, implying she is a polytheist or an atheist), then it is not permissible to continue a relationship with her.