Jisoo. She is the onewho does the scolding of Rose and Lisa , and she's the one who is most informed on what is appropriate/inappropriate in Korean culture. Jenniefrom what we've seen seems too laid back for a leader position.
I could see it being either Jennie since she speaks up about things and has strong opinions, or Rosé because she turns into a different person when they need to get serious. She’s also well spoken.