I had a great time there for a few months, and my friend and I (both female) mostly just backpacked around and slept in hammocks on random beaches. I felt very safe, safer than in big US cities (but maybe not quite as safe as small country places).

I think you just need to be careful in terms of keeping your valuables near you. Like in this case, she might have been safer if the roommate just took the wallets and such into the bathroom with her, or putting them in random hiding places so someone who came in the room really fast wouldn't find them.