Yet her friends say that she got into the car willingly. That blows a big hole into your GHB theory.
She knew the boys casually..it was reported..so they slip her one..she's malleable..they steer her off..figurte it's her last night on the island..she won't make a scene..justr get on her plane tomorrow..it makes some sense..
if we believe the internet rumour, it sounds to me like this girl and perhaps her friends have been hanging with these guys for more than just that night, which would explain why she may have felt she could trust them, the Dutch guy looks like he is only about 20ish, about the same age as these other kids, ie by that time they weren't strangers...or they didn't seem like strangers - usually if guys are real creeps that manifests itself pretty soon, though not always......she may have gone off with these three guys before and they were well behaved gentlemen, maybe some of the kids on the trip have vouched for these guys?
If, as the witness says, she got into the car with one man behind the wheel...and the other two were ducked down, as if hiding in the back seat, then she didn't know she was going off with three men.