Inalcanzable means 'unattainable' or 'unreachable', a perfect word to describe someone who seems out of your league.
In the song, Kali Uchis sings about an angelic woman who is a 'princesita inalcanzable' (an unattainable little princess). This powerful adjective paints a vivid picture of someone who is so special they are almost untouchable, setting the celestial tone of the song.
This song is a beautiful tribute to a woman who is so pure and strong she seems almost otherworldly. Kali Uchis and Peso Pluma describe her as looking "igual que un ángel" (just like an angel), someone whose home is in heaven. She's been through a lot, and the lyrics say "Le rompieron el cora'" (They broke her heart), but she never lost herself in the process. While everyone else is chasing "plata" (money) or "fama" (fame), she just wants calm and to protect her soul.
What makes her so special is that she's a rare kind of person. The song repeats that a heart like hers "está en extinción" (is going extinct), making her seem precious and unique. She's called "La favorita de Dios" (God's favorite), a heavenly being who is simply too good for most people. As the lyrics warn, "El que la quiera, que rece" (Whoever wants her, let them pray), because a woman like this is truly one of a kind.