For a short visit, I'd recommend Lana'i and the FS Manele Bay. I was just there for July 4th weekend - it's a phenomenal hotel and a beautiful island. For a short getaway, everything you need is right there - no rental car expense as their shuttle will take you to town or up to Koele.

If your GF lives on Maui and has proof of residency (drivers license), she can book greatly discounted 'Kama'aina' rates at any FS property (and many non-FS properties) and the ferry between Lahaina and Lana'i is discounted as well.

She will need to call and book the room in order to get the discount - which is sizeable and often includes other amenities.

If you want the Big Island, the FS Hualalai has great Kama'aina deals which include buffet breakfast for two - that alone is worth about $90 a day in value.