Urge your friend or relative to seek the help of the elders. If he or she does not do so within a reasonable period of time, loyalty to God should move you to report the matter to the elders.
وَأَنْتَ تُرِيدُ أَنْ تَبْقَى وَلِيًّا لَهُ ،‏ لَا سِيَّمَا إِذَا كَانَ صَدِيقًا حَمِيمًا أَوْ قَرِيبًا لَكَ .‏