Just a couple of observations about your daughter's plans:
1. If they hike, they probably know how to research hiking options. Here is an important one in Hawaii:
https://htmc1910.org/
2. If they are really planning on sleeping on the beach, they should be aware that their neighbors are likely to be indigenouse homeless who may not show hospitality to those "beaching-it" for their vacation.
3. Don't keep valuables in the car. There are predators who love to burgle cars left at trail heads and beaches.
4. October can be prime-time hurricane season. If your daughter is planning on going into the mountains for days at a time, make sure she keeps track of weather forcasts.
5. My number 1 place to hike and camp is
https://www.tripadvisor.com/Attracti...ai_Hawaii.html