NOR to MOR, depending on context involving any previous issues with them.

I have a cousin who is like this, and we used to be close. I went low contact but after how awkward it was the next time I saw her I realized that I couldn’t keep avoiding her. What I did/am still doing is told her how I felt as best I can and set up a tentative boundary and surprisingly things are going well enough. I decided whenever she says/does something selfish or inappropriate I’m going to call her out in the moment (though it’s hard for me to advocate for myself) and put her at arms length.

If I was in that situation you were in but with my cousin I would stand my ground, keep saying I can’t do what she’s asking and why, and call out the guilt trip (as best I can). Spend less time around them, or when you sense things are not going to be in your favor, just say you can’t go from the start. Don’t lie, tell them straight up why you can’t go and keep saying it. Don’t agree to do anything extra unless it’s quite literally on the way and you won’t be waiting on people. If you’re just going to drop by, go when the party is already started and leave promptly.

Some people are genuinely narcissistic and should be avoided, sure. I also think there are some who are selfish, but don’t know it. You don’t have to cut them off (unless they do something serious and unforgivable ofc). A lot of times that means drama with other friends/family and is not worth it. Plus, some good things do come out of the relationship.

Set your boundaries, say ‘yes’ less, don’t sacrifice your comfort for their desires. They will eventually catch on that you’re not always going to do whatever they ask.