Last year I had some Aluminum rod, and I made some Harpoons out of aluminum because it was quick and easy and the season was upon us when I was doing it. Each time they got dropped on the deck point first they were no longer sharp

They touched up quick and easy with a file, and I had no problem with them working.
This winter I have made some out of Stainless, they are much tougher and will work fine.
There is fancier stuff out there, its harder to work but it sounds like she has some access to some quality tools.
No matter what its made of, odds are somebody is gonna drop it over the side of the boat and no matter what it is made of, it will probably sink
You can see the rant thread by Corrirod about those that think you need the latest greatest gucci equipment to catch a fish.

Standard steel will work, it will get rusty and need cleaned up before each trip, but it will work.