Curvilínea literally means "curvilinear," describing something composed of or bounded by curved lines. It's a sophisticated and less common adjective than simply "curvy."
In this song, Nathy Peluso uses it to describe herself as "Una perra sorprendente, Curvilínea y elocuente" (A surprising bitch, Curvilinear and eloquent). She reclaims the word "perra" and uses "curvilínea" to powerfully and elegantly assert her physical presence and confidence, making it a memorable and empowering descriptor.
Nathy Peluso walks into Bizarrap's booth and spends the whole session refusing to be talked down to. Her verses are one long self-portrait: curvilínea y elocuente, colossal, extravagant, an animal. She is funny about it too, calling herself a desayuno continental and insisting you listen with an apron on. Under the jokes a real line is being drawn. She decides what happens next, she is not thanking anyone for the attention, and she is very clear that the confidence is hers rather than borrowed.
The chorus is the sharpest part and the easiest to follow: manda mensaje, dice que dice, pero después no hace ni 'mmm'. He texts, he talks big, and then face to face he says nothing at all. That is the target, keyboard bravery, and her answer is venime de frente, come at me in person. One thing worth knowing before you listen: Peluso is Argentine, so you will hear tenés and venime where you might expect tienes and venme, plus English words dropped in mid-line for the fun of it.