The Dutch kid probably raped her then killed her and took her to the point where the sharks feed and disposed of the body. Nasty, yes but I think that is the reality of it.
Sadly.....
If her body would have made it to Venezuela, it would have found it by now.
At first I figured all three of them raped her and she died on her own, probably from the rufies, happens all the time, then they had to dispose of the body. They were probably pretty angry with her for dying on them. By Occams Razor that's probably what happened. The plan was probably to leave her knocked out on the beach so she'd wake up hung over, embarrassed, used, and knocked off her high horse (chastity) with no time to do anything but get her stuff and get on the plane and go home. Plans have a way of going awry.
I wish they'd fry. I hope they all meet some big bubba named Gilles who'll teach them something about being the smaller, weaker one.