The sister is undoubtedly well aware of the strategic balances between NK and the USA, and NK and SK. Absent the nukes, NK would be an Asian Albania, and not much more of a threat than Albania. She is also undoubtedly well aware that China provides a great deal of support to NK, and China doesn't want another Korean War.
Got news for you...this woman will never become leader. Just not going to happen. She surely advises her brother, but her brother is in charge. NK is still very much a male-dominated society. SK is also male-dominated, but somewhat less so than NK.
In my opinion, her public utterances are a signal that NK wants to talk with the Biden regime. What concerns me is who Joe might have talk with them. Joe can't do it. Harris...no idea. Hope someone competent is doing the backchannel communications. At the rate things seem to be going, all the gains made by President Trump are likely to be frittered away. That really eats shit, and could cost lives.