Diablita literally translates to "little devil" (female). It comes from the word diabla (devil), with the diminutive suffix -ita added to make it sound smaller, more mischievous, or even affectionate.
In the song, this playful slang is used to describe the woman's transformation. After being betrayed and heartbroken, she sheds her innocent image and embraces a wild and seductive side, becoming a diablita who is now in control of her own desires.
This song is a total anthem for anyone who's been done wrong in a relationship and just wants to go out and have a good time. Anuel AA kicks it off by explaining the whole situation: a woman decides to be "mala y no quiere dueño" (bad and doesn't want an owner) because "un hombre la engañó en su vida" (a man cheated on her in her life). The old, "good" version of her is gone—"la buena es la difunta" (the good one is the deceased)—and now she's out to party and forget.
The chorus is super direct and tells you everything you need to know: "Ella quiere beber, ella quiere bailar / Su novio la dejó y lo quiere olvidar" (She wants to drink, she wants to dance / Her boyfriend left her and she wants to forget him). Anuel and the legendary Romeo Santos step in as the guys she meets on her night out. They describe her transformation from a quiet girl to pure "candela" (fire), ready to get revenge on her ex by having fun with someone new. It's all about her taking control after being hurt.