'Very mindful, very demure' is a viral 2024 TikTok phrase from creator Jools Lebron, who used it to describe a modest, considered, low-key way of presenting herself at work and in public. The catchphrase swept the internet for months and became shorthand for any restrained, polished, gracious behaviour — often used self-consciously and humorously. If your teen says it, they are quoting a hugely popular meme. Wholesome and harmless.