Chamaquita is a diminutive of chama which is a colloquial term, especially in some Latin American countries like Venezuela, for a young girl or a chick. The diminutive ending -ita adds a sense of smallness or endearment.
In the song, it's used to describe the protagonist's transformation from a "good student" little girl (chamaquita buena nota') to a rebellious adult. It highlights the contrast between her past innocence and her current lifestyle, making it a key word for understanding the song's narrative.
Quevedo and Juseph paint a picture of a young woman who has completely transformed from her childhood. Once a top student, she now lives a rebellious life, the total opposite of the "little girl" her strict parents think she is. She sneaks out her window to party, turning every day of the week into a weekend. The lyrics describe her as someone who looks like a model but has very short-lived relationships, lasting only "fifteen seconds like a Reels [video]."
This wild lifestyle, however, isn't just for fun. The song reveals a deeper, more painful reason for her behavior. She goes out drinking and smoking to numb a deep "wound that doesn't heal." Her partying is a way to escape from an inner sadness, making her a complex character who is both the life of the party and someone hiding a secret pain.