Definitely Maui or Kauai. We stayed at the Sheraton on Ka'anapali Beach last year. Great time! It has been totally remodeled and is a very nice place. There is also a Marriott and a Ritz on the same stretch.
I understand that Molokai has a really nice resort on it. Less people.
The big island of Hawaii is nice. The lee-ward (sp) side on the Kona Coast is awesome and there's some kick a$$ fishing. If she likes sport fishing.
No Honolulu unless you like big schitties and lots of crowds.
We went to the Grand Wailea south of Keihei, Maui for drinks and dancing and it was realllllyyyy fancy. That place did have some nice restaurants and clubs. It also had great shopping!
Sometimes the big fancy resorts have stuffy old people. Be cautious.
HAVE A GREAT TIME!