She was more like a helpless child. In all of the other iteration she is a lethal tactical genius and a hardened war veteran.

But with a helpless child inside her, at the core of her personality, because her traumatic transition into a brain in a robot body robbed her of the chance to actually grow up. That's the whole point of the character. She's psychologically stunted, despite her military capability. She can't lower her defenses and interact on a normal social level, as a result. At the same time, she's also never quite comfortable in her own mind and body, for the same reasons.

Batou is the only person in the story who comes even close to understanding this, which is why they have a unique bond.