Funny, I posted here about my narcissistic FIL not too long ago in this very forum. In our case, I got to a point where I was sick of him being so disrespectful to me and laid down a boundary with him (with the support of my DH). He reacted badly and told me that he disagreed with me, he does nothing wrong, it is all in my head.

I was totally sick of their games and manipulations, so I said that unless he can respect that boundary, then I can't welcome him into my home. He threw the biggest hissy fit temper tantrum you can imagine and that was that, I haven't seen him since. That was like 8 months ago. There have been passive aggressive emails & phone calls from him & MIL to me and DH, all launching a huge attack on me for daring to tell him that he isn't perfect (in a nutshell). Every emotional trick has been pulled, from them crying to raging to attacking my character to saying they can't talk to me anymore because I "terrify" them. (Really, it should be the easiest, most basic boundary to follow, that this overreaction is just beyond belief.) It's been really rough at times, but I am holding firm, for the health of our whole family.
Some days I like to read the beginning of the serenity prayer (and I'm not even religious) because it helps me stay clear on how much energy to put into this: "God, grant me the serenity to accept the things I cannot change; courage to change the things I can; and wisdom to know the difference." Because that in a nutshell is what you need to do to deal with a narcissist. Put your energy & courage toward what you CAN do--like read the books above, draw healthy boundaries, hold to them--instead of putting it on things you can't, like the narcissist's behavior towards you and their sick family dynamics.
Also, remember, any time you confront a narcissist you are going to trigger that bottomless pit of narcissistic rage. Their egos are fragile/non-existent, despite their bravado, so they just do not have the ability to take the slightest criticism. Insight into their behavior and motives is rare--or very shallow. They usually are full of rage and/or depression, so it is easy to lash out at you if you try to upset the status quo or question them. Just beware that for your MIL to be functioning with her family, there are people near her--like children & spouse--who have lived for decades with this as "normal." It's pretty common for those people to want to protect the narcissist and the dysfunctional system, so you won't just be stirring up your MIL's rage but also
they may attack you to defend her. (Like what happened to me!) That's really common in a family with a narcissist, so it's good to chose your specific battle carefully if you're going to go the confrontation way.
The other choice is to slowly distance yourself from them until you rarely see them. That was my previous tactic, but those rare visits started getting too traumatic for the kids and I had to take a stand. Hope that is the kind of info you're looking for, you can PM me if you want to talk.
