Why do narcissists accuse the victim of being a narcissist?

[Recoverellie]

An ex friend who turned out to be very covertly abusive has told all our mutual friends, staff at school and pretty much anyone who will listen that I'm a narcissist. The worst part is, many believe her and I've been ignored ever since.
Why do they do this? Why can't people see the truth? The whole situation is making me want to move away, sadly not an option right now.

To deflect from their own poor behaviour. Just hold your head high, OP.

Google DARVO

Ex Dh did exactly this. Fortunately the only poor deluded souls that believe him are his family.

Anyone who gets close enough to this person will eventually get the treatment you did. Hold your head high and concentrate on the friends and colleagues that are truly good friends.

I could have typed this myself.

And added his new girlfriend to the list.

They're projecting. It's easier to project their crap onto you than it is to acknowledge they're at fault. They're narcissistic, they're clearly incapable of being at fault.
Sorry to hear you're going through this. Usually people will see through it in time but I appreciate that's not going to make it better for you right now