Vanentina

my narc sister (she is an uber-rich, high society girl who owns multiple residences in new york city, in the hamptons, in other locations looked upon by the rich as acceptable parking spots, she has her own fashion line, knows everybody on the circuit, goes to all the best parties, is a perfect looking person having access to better plastic surgery than you've ever seen in hollywood, etc. etc. etc. doesn't it sound so terrible)

My Nsis is also powerful and confident.

So, taking all that into account do you believe she is;

A wounded soul, a secretly insecure frightened person. A terribly hurt depressed person hiding behind a facade of confidence?
This seems to be an explanation for Narcissism many repeat.

Sounds to me your sister is having a great time!

NPD mask. What does that mean?

They are what they are.

Dont we all wear a bit of a 'mask' when we go out.