Which is what grey rock does. The one worst thing you can do to a narc is deny them narcissistic supply. That hate it, they need power and control and grey rock is denying that. They feed on all attention both good or bad, anything you to to attack them will be used as supply. Deny it, but do it in a way that they can’t twist to be your fault.
Sort of… do magick, and know beyond a shadow of a doubt that it works. Do not pray, hope, believe or think, but know. Otherwise your doubt can kill the magick and if you know you’re going to doubt you might as well not bother.
This is a magick forum If you wanted other advice I’d say see a therapist, they are qualified to help you deal with these people in person.
Law enforcement needs more then feelings, if you have evidence or a witness report it to the police and encourage any victim to testify and that you’ll support them as needed. Otherwise this is not a subject we can help with. You can do magick to help with that too.
After you make sure you have banished anything unwanted summon Valac of the Goetia and he can reveal betrayal: narcs betray people and they always lose because of it, so here this just accelerate the natural progression before it causes too much damage, hopefully. Get Valac to reveal to your parent what this person really is, get them to reveal themselves over past betrayals (including abuse situations) for a police investigation.
We don’t moralize here so you don’t need to justify what kinds of magick you want to talk about. This is a “working thread”, and the rule is clear for a working thread. Otherwise all out baneful magick thread would be diluted with well meaning derails into questioning the OP, and we don’t do that here.
Well you could just do a death curse then. Even when these fail they remove the person from your life as if they were dead. But you probably have enough beef with them for it to just kill them.
I had the impression you wanted them to suffer and death would stop that, or I’d have just suggested it earlier.
Handy death curse thread with multiple options:
I know the feeling 
It’s all good!
I don’t believe in it, at least not the way it gets colloquially used in the West. As far as I can tell, karma is a way to discuss what I see as probabilities and flows of energy put in motion via energetic relationships between spirits (i.e. humans who are spirits incarnate into a human body). This makes “karma” optional when you know how to manipulate energy, which is what the entire point of magick is. It becomes a way of reminding us of our complexity and that we are sharing this world with other energy beings that also change the energy flows based on their feelings and desires, and that as we are immortal, so those energetic relationships can also remain between incarnations. But they are a consequence, imo, not a cause, and that’s where the concept gets misused as an excuse.
So this:
… is unlikely. They don’t feel that have done any wrong and it’s not a punishment anyway… but the consequence that they eventually piss people off and have to move on and make all new friends who don’t know them as a result is natural. But no, you don’t really want to wait for that. They will work very hard to control the person who has that power (your parent) to make sure they stay under their sway, it could take years.
And all that time you’re just doing Grey Rock to stay safe and sane until you can move out.
Yeah I’d bind them first and also death curse them myself, in multiple rituals that complement each other in intent, which is called “layering”.