It is important to remain calm when dealing with “flying monkeys,” who are people sent by the narcissist to harass and intimidate their intended target. The best approach is to remain strong and not to engage. Try to make it clear that you don’t appreciate the other person’s tactics and that you don’t wish to be bothered or harassed.
It may be helpful to state this firmly, but without hostility, so that it is made clear that such behaviour is unacceptable. It is important to be aware that the narcissist will likely continue to send flying monkeys, and know that it’s best to ignore them and not engage in any kind of retaliatory behaviour.