Why would she belive that? she knew who Deepak his brother and Joran were, from talking with them in the bar.
I am not blaming Natalie, but what she did is make a huge judgement in error.
Since I have been out of the bar scene for quite sometime maybe it's the norm now that when you leave a bar 2 sheets to the wind as a woman you get into a car with unknown drunk male occupants.
She believed that because she was only with Joran and he says himself he only saw her drink one drink which he may have drugged.