Living for this means loving something intensely right now. "I'm living for this song" = I'm obsessed with this song. Very common across TikTok, Instagram, and Twitter. The phrase has roots in Black queer slang from the 1990s ballroom scene. Not concerning at all; it is enthusiastic praise. Often used about food, fashion, music, and TV moments. If your kid uses it constantly, ask them where they first heard it, not to police their speech but to understand which online community they are in.