I think what is required for an intervention is that the group that is doing it be in complete agreement as to consequences AND that something is available for the person suffering in terms of help RIGHT THAT MINUTE, i.e. “We love you and we will always pray for you. But if you do not pack your bag, get into the car and leave right NOW for in-treatment therapy for your problem we will no longer accept your telephone calls, loan you money, invite you to dinner etc.”.
I used ‘in-patient’ as an example - I suppose you could set up a therapy appointment for them and say “If you do not go to this appointment and then continue to see this therapist for (pick a number - say ten) sessions then the consequences will be…”.
It would seem to me that you could stage an intervention for any issue - the tough part is getting everyone on the same page, providing the immediate help and then sticking to the consequences if the person says “See ya”.