What is the ruling of the Shari'a regarding the question, "Am I a dayyuth?" and what should I do, given that advice is futile with my friend who loves another man besides her husband and wishes to marry him in the future?

Whoever witnesses a forbidden relationship between two non-mahram individuals must not remain silent, for that is a great evil. They must enjoin good and forbid evil, in accordance with the Prophet's (peace be upon him) saying: "Whoever among you sees an evil, let him change it with his hand; if he is unable, then with his tongue; if he is unable, then with his heart—and that is the weakest of faith." Therefore, the woman involved in the relationship should be advised. If she does not respond, she should be threatened with reporting her to someone who can put an end to this forbidden relationship.