My instinct (which is worth nothing because we will never know for certain) is that she is guilty because if they really wanted to set someone up, you’d think they would do it with something harder and higher quantity. Unless they thought about that angle already and went with the vape specifically for that reason
Also, look at how clueless the average traveler is and it’s not surprising that someone could forget something like this. I think the same way if I were going to Russia, China etc- I used to throw my bag in the washing machine before packing for international trips