Que le muerda is a fiery Spanish expression that literally translates to "let him/her bite it." It's a powerful phrase used to show defiance or indifference to someone else's jealousy or anger.
In the song, Becky G sings about moving on and thriving after a breakup. This phrase is directed at her ex: if he's upset seeing how great she's doing now, that's his problem. It's a sassy and empowering way of saying "let him suffer" or "let him eat his heart out."
This song is the ultimate post-breakup glow-up anthem. It's all about that moment you realize you're so much better off without your ex and you want them to see it. The whole mood is set by the title and chorus, "Que le muerda ahora / Verte dónde estás" [Let it bite them now / To see where you are]. It's a very direct way of saying you hope they feel a sting of regret when they see you thriving.
The lyrics list all the ways she's moved on and is living her best life. She's active on social media, wears expensive perfume, and pays her own rent without help: "Paga su renta sin pedir fiao'" [She pays her rent without asking for credit]. She's even had a spiritual cleansing with a santero and is listening to new music. The song makes it clear this isn't a temporary phase; she's fundamentally changed for the better, telling everyone, "No es la misma, ya está curá'" [She's not the same, she's cured now].