I'll venture in here but must first confess that I haven't studied much psychology and most of my education in it comes from Jane Austen. :-).

It seems reading your list that I would attribute different ones to each Marianne and Willoughby.

Marianne...
self important
fantasies of ideal love
believes she's special
sense of entitlement
haughty (highfalutin was a familiar term listed under haughty and made me laugh)
lacks empathy (especially shown in her treatment of Elinor)

Willoughby may be these (but I don't think Marianne is these three)
requires excessive admiration
inter-personally exploitative
envious of others
arrogant?

They seem to share these qualities:
lack empathy
sense of entitlement

It's harder to know what's going on in Willoughby's mind. And perhaps it's hard to separate the behavior they encourage in eachother, and to know which qualities are independent of their relationship if that makes any sense.