NPD GC sister told everyone at my party to go to her house instead, why?

[Blueberry Pancakes]

I have been NC with my GC NPD sister for one year. We are both full grown adults. As I unravel things she did to me through the years that I thought at the time were just stupid, I think now were instead displays of her NPD. Can anyone advise if I have correctly identified her behaviors as possible NPD? One situation a couple years ago was when some childhood friends we both knew were in from out of town. I offered to host an afternoon brunch for them, and invited my sister (at their request - not mine). She told me that she already had plans with friends, but might stop by briefly if she had time. She asked me to call her back with specific time and details when the date got closer. Of course, nothing is easy with her. So I called the night before and told her the exact time and when food would be served. She said she could not talk because she had to preserve her cell phone battery and to let her know if there were any changes in my plan. I do not know why she repeatedly asked me to give her the same info. Anyway, I left her an email with the details and said "come over if you can".
The next morning my phone started ringing and it was her calling. I ignored it because I was getting ready for the brunch and I had already given her the details she needed. She continued calling my phone repeatedly for an hour. My friends arrived and the brunch was great and we were all having a nice time. Two hours later my sister arrived. She was mad I did not return her calls that morning and said she had no idea what time to come over. I told her there was no change to what I already told her and to read her email where I confirmed. She just rolled her eyes, and then began socializing with everyone.   
She started having a good time and enjoying their company. After about a half hour she started telling everyone to leave my house and go over to hers. She lives about 10 minutes away, and wanted to show everyone the new deck she just had built. Fortunately, nobody wanted to leave and one person even exchanged an odd look with me and turned to my sister and told her "No, I think we are fine staying here." My sister obliviously shrugged it off and continued basking in the glow of their attention until the party was over.
My sister did not even want to come to the party I was hosting, then she tried to move it to her house when she realized we were having a good time. What the heck is that about? She has done this many times when I was doing something good, then she wanted to take it for herself. I sound like a childish kid, but I think her behavior reflects something more than just being immature.
 

[bloomie]

Blueberry Pancakes - this sounds like rivalrous behavior and it doesn't sound childish at all that this is an example of an underlying inability on your sister's part to engage in trustworthy, reliable, loving and supportive relationship with you.

A life time of this kind of thing can really stack up and is very hurtful and causes huge disconnect in our relationships with siblings or family members who engage from a position of harmful rivalry and oneupmanship.

Processing these experiences can be really painful and sometimes self doubts creep in. Trust yourself and continue on this healing journey!

[athene1399]

She started having a good time and enjoying their company. After about a half hour she started telling everyone to leave my house and go over to hers. She lives about 10 minutes away, and wanted to show everyone the new deck she just had built. Fortunately, nobody wanted to leave and one person even exchanged an odd look with me and turned to my sister and told her "No, I think we are fine staying here." My sister obliviously shrugged it off and continued basking in the glow of their attention until the party was over.

I feel there's a few things going on here. If she's diagnosed NPD, there's a big chance she likes feeling superior: "Please some see my awesome deck and tell me how great and amazing it is." Often that need for attention and for others to pat them on the back for accomplishments in really to hide their vulnerabilities or insecurities (in general. not in every case of NPD). If she is the GC, she may have become NPD by being told how great she is, which would mean possibly she just feels deserving of the attention and her entitlement is driven by other things. She could have been jealous that they were having fun at your house and wanted to feel good about herself by being able to move the party (Which didn't work out for her). It's hard to tell for sure without actually being her T.

But I think something good happened here too. No one left your party. i think that's a good thing! And they gave you the looks that said "What is up with your sis?" That must have felt validating. Sometimes others can't see through the PD mask and that can be very frustrating to those who are Out of the FOG.

And in my experience with people with PDs, they often act childish.