Is it permissible to continue a relationship with a young man who speaks of love, infatuation, and sexual relations, and threatens to return to sins if marriage does not occur, and does the girl bear the sin of his return to sins if she leaves him?

The girl must cut off the forbidden relationship with the young man, because it is an act of disobedience to Allah Almighty, a falling into the footsteps of Satan, and a danger to the girl that may lead her to commit the abomination of zina (fornication/adultery). This young man is not worthy of marriage due to his disregard for prohibitions and his deception of the girl with sweet talk and false promises.