Keep in mind all these young ladies that have died throughout SE Asia is recent years by mysterious poisonings, were not robbed, nor sexually assaulted, so unless there is a madman running around SE Asia poisoning 20 something women, I thinks its some exotic mix of drugs doing it. If the family is have any idea, they need to have the autopsy done in North America, period.
These seemingly nice and normal young ladies, all could be a tad naive too, and trust people they should not, and use all sorts of drugs that are illegal, and easy to access in SE Asia, especially, the backpacker circuit.