I think I still need to get to that point. I'm towards the end of chapter 9 (airship rescue). Has the event in the bolded already occurred and I didn't pick up on it or is there a grand betrayal soon?
It's been hinted at thus far. When it happens, you'll know. It will probably piss you off. It pissed me off.
I remember looking back at Vanielle, her constantly overly happy attitude, her bubbily nature and when you learn her back story and figure out why she's there and why she's doing what she's doing, seeing her as the saddest person who, this whole time while keeping the spirits of everyone up, was a hair away from breaking herself.
And then the thing happens and it's like, "Oh. She was just annoying. NEVERMIND THEN!"
Square has never really known how to make these kinds of characters important, but they do know how to make them interesting, which is why Vanielle is so disappointing. But at least she keeps you guessing.
Lightning has the worst character arch in FF13. Sazh, Vang, Snow, Hope, Serah, they're all 1 dimensional and single tone, but they're at least consistent. Lightning changes attitudes and demeanors dramatically, for no reason, to the point where I thought they were implying she had mental problems.