What the hell?
Thinking about this for a moment, it seems clear it was a suicide. There's no way anyone on a short (2 hour) hop from Korea to Japan could fail to notice two people entering a bathroom...
But I've got to wonder: How did she do it? Having been in my share of airplane bathrooms, I've gotta say you're a clever monkey if you can figure out where you can mount a ... rope? WTF, did she have a length of rope in her purse or what?
Mysteries. The world is full of 'em.