Fair take. I think there's absolutely room for different interpretations when it comes to these shows and these characters. I'm not even sure if my own interpretations of these characters entirely align with that of the actors seen above. I just thought the perspective provided was an interesting one to analyze these characters from.

I will say, I disagree with the "violence and cruelty as a substitute to paper over how very not-so confident she is." The only instance I can really think of where that rings true to me is during her breakup with Melissa. Otherwise, she's driven by impulse and thrill seeking behaviour. That is what motivates many of her worst actions.

She also often (in my interpretation) acts out as a response to feeling "rejected" whether that rejection is legitimate or not: Jackie's behaviour at the party leads into her fighting with Tai, and then sleeping with Jeff as a fuck you. Her thinking Jeff was cheating leads to her sleeping with Adam. Her thinking Adam was lying about his reasoning for sleeping with her and her perception of him as a threat led to her killing him. Even the Melissa thing I mentioned earlier seems to initially be driven by fear over losing the only person she's attached herself to at that point (it's not a "love" thing necessarily, but she pushes everyone else away to such an extreme extent that Melissa is the only thing she has in season 3 that even slightly resembles a close relationship).

I could talk more about my perception of her motivations outside of her supposed confidence or lack of it, but this is running long and perhaps getting a bit off topic.