Some people have a lot of tenacity, so sometimes it works to ignore, sometimes it does not and it just makes it worse, in real life I have learned narcissists hate being ignored.
Having said that they will often find another victim but until they do they may persist.
Off topic I guess. Hopefully what you state tends to be the most common result.
With a narcissist you thank the Lord for opening your eyes to them. Then you ignore them by doing this you take the power away from the narcissist. Nothing good will ever come out of being around a narcissist so I would say cut them off completely.