R, we're kindred spirits when it comes to rustic. In fact, as a solo traveler and buddy-less diver, I've made almost all my own arrangements to get off the gringo-beaten track. This discussion and the other threads about the operator, boat provisions, etc., certainly are a tragic reminder for those like us. Perhaps the parents can take some comfort in knowing that the young lady exited full of energy and purpose, as she apparently lived her life.
Having said that, I think you're more right than you realize in your last sentence. Vacationing gringos shouldn't be able to define the trip's destination nor conclusion. In the other threads referenced by Hank, on SB and in the Belize dive forum, hearsay has it that these divers insisted on going on to the original destination despite weather warnings (and one presumes, crew warnings.) As a very long-time traveler to 3rd-world countries, I've seen too often the power of the culturally arrogant dollar that pays for *your* terms, local custom or conditions notwithstanding.
Last but certainly not least important, there was a heckuva quote on one of those other SB threads, to the effect of "don't abandon the boat unless you're stepping UP off it." That's a powerful thought for us all, too.
--Wayne