If they aren't sightseeing around the island, but mainly staying at the resort, she will be wearing her swimsuit and coverup most of the day. At night it does get a little cool so bring a sweater or hoodie. Island wear when sightseeing, shorts and tees or camisole/tank tops. Flip Flops or slippers as they call them in Hawaii, are day and night wear, we usually take sandals. For the beech and swimming in the ocean recommend beach shoes because of sharp rocks or coral. They sell them cheap at the local Kapolei Target. Nice casual at night, sun dress, or a sleeveless dress or nice crop pants with pretty top. One pair of crops with a few tops would work for a weekend.