I believe that's "hang loose". She's a Hawaiian, and a surfer. And yes, it too is Hawaiian.

Shaka sign:

The shaka sign, sometimes known as "hang loose", is a gesture of friendly intent often associated with Hawaii and surf culture. It consists of extending the thumb and smallest finger while holding the three middle fingers curled, and gesturing in salutation while presenting the front or back of the hand; the hand may be rotated back and forth for emphasis.