Me doblo literally means "I bend" or "I fold". It's a powerful phrase that ROSALÍA uses to express emotional vulnerability and breaking her own rules.
In "COMO UN G", she sings about being tough and guarded, like a "G" (gangster). But then she confides, "Ni escribo canciones de amor, pero en esta me doblo por ti" (I don't even write love songs, but in this one, I fold for you). This confession is the heart of the song, showing that for this specific person, she is willing to let her tough exterior crumble and "bend" her principles.
This song is all about trying to be tough after a breakup, but not quite succeeding. ROSALÍA starts by laying down the law: "Si no lo puedes tener lo tendrás que soltar" (If you can't have it, you'll have to let it go). She insists she's fine on her own, wishing the other person well but making it clear they're separate now. She even says she's so detached that she might forget their birthday, which is a pretty cold move!
The whole idea is that she's moving "como un G" (like a G), which is slang for a gangster—someone tough who doesn't get emotional or fall in love. But then she completely contradicts herself. She admits, "Ni escribo canciones de amor / Pero en esta me doblo por ti" (I don't even write love songs / But in this one I'm bending for you). The song ends with her promising to always love this person, even if they can't be together, showing that beneath the tough exterior, she's still completely devoted.