Well I'm not Whisperer, but I'll give you my take on it.
If JI is passive aggressive, which I believe he likely is, the very definition of that is a learned helplessness. Passive aggressives are likely to sit back and let it appear that they are being controlled, but really they are the ones controlling the situation. The frequently blame others. . .well, I can't do this because so-and-so is doing that. It's not true, but they try to make it look like the other person is to blame. It's the "passive" part of passive aggression. . .make the other person look bad. Just think about social passive resistance. It's effective because those resisting do nothing, while they let the others make themselves look bad. . . think 60's civil rights sit ins.
As far as the "no personality" and temper. That is often how it is. Anger comes from fear. . .fear often from low self esteem. . .that can often mean loner or someone who isn't very socially inept. . .maybe even seen as shy.
I don't think DB is abused. She is emotional though. I do think she is a bit of a drama queen and gossip. She definitely cares about what others think of her. That doesn't mean she has to be the one calling the shots. JMHO