Not necessarily.  It's a question of prudence.  Do you think that there's anything you could do or say that would make a difference?  If not, then you could try to do little things gradually that might make the faith appealing to someone.  But no one can give you specifics about what to do or to say unless they know the situation.  Ex-Protestant, atheist, Novus Ordo, Catholic fallen away morally?  Those all entail different approaches potentially.  As St. Thomas taught, you're not obliged to "rebuke the sinner" if you're morally certain that it won't make any difference, and it can even be a virtue not to rebuke them if you think it might even make matters worse.