Malilla is a colloquial Mexican slang term that's far more expressive than simply saying "sick". It comes from malo (bad) with the diminutive -illa, adding a nuance of feeling vaguely unwell, down, or hungover.
In this song, the singer contrasts his ex's calm demeanor with his own state: "Qué tranquila se te ve / Y yo bien malilla". It brilliantly captures the emotional and physical crash of a heartbreak hangover, making it a fascinating and culturally rich word for learners.
This song is a classic breakup anthem, but with a twist. Peso Pluma starts off feeling pretty low after a girl was unfaithful. He sings, "Maldito cariño, era todo una mentira" (Damned love, it was all a lie) and admits it feels terrible to start and end his day without her. He's drinking whiskey again, something he says he hadn't done for love in a while.
But don't feel too bad for him, because the mood changes fast! He calls her his "peor error del año" (worst mistake of the year) and then immediately starts listing all the ways his life is better now. He's flying in private jets, driving a new car, and hanging out in Malibu with a new girl. It's a song that goes from heartbroken to bragging, telling his ex exactly what she's missing out on with some very direct language.