Your best resource for what happened during those times are the people who lived through it, and the most complete resource for that would be with the veteran societies.
Maybe these links can bring some clarity for you.
https://www.100thbattalion.org/history/stories/nisei-soldiers-hawaii/
This article illustrates the history of Japanese in Hawaii up to and during WWII. There are links that you can explore to learn more about specific personal experiences.
The Nisei Veterans Memorial Center has been building a collection of oral histories of veterans and their families. If you ever visit Maui, it's well worth a visit. Their archives are already quite impressive and always growing. I hope you'll find the section titled '10 Facts' interesting.
https://www.nvmc.org/about/
During WWII, the Japanese population made up a significant portion of the work force in Hawaii. Big business would have had a very hard time dealing with an extreme labor shortage during wartime. Martial law was in place.. the airports and harbors were locked down.. and the beaches were patrolled nightly by military, police and fire, and volunteers. As a result not a lot of people were confined to camps, but small camps were established for hardcore issei loyalists and other suspects.
It seems that your grandmother was nisei.. American born, but raised with the customs and values of the Japanese culture. She would not consider herself nor would she be considered a Native Hawaiian.
As far as personal property being stolen... you should research the internment camps on the mainland. Japanese Americans were rounded up and put in internment camps and their houses, businesses, farms and ranches were sold off before they returned. A real disgrace and a black mark in American history.
I wish you luck in your quest.
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