I guess my six items would vary depending on how I was to get to said island.

If I am being taken there and will be picked up in a known time, then my six would be:

Enough water for the planned time
Large blade like a kukri or golok
Ferro rod
Cordage (as much as I can take)
Tarp
Metal pot

If I was being stranded there somehow, I would swap the pot for a personal locator beacon.

I ultimately would want to get off the desert island.

Good luck to your wife on her contest.