Alfombra literally translates to "carpet". It's an interesting word choice because it's not commonly used in song lyrics, especially in such a metaphorical way.
In the song, Paty Cantú sings, "Creí que yo era alfombra para que pisaras" (I thought I was a carpet for you to step on). This powerful metaphor conveys a sense of being walked all over and taken advantage of in a relationship, making it a memorable and emotionally resonant word.
"Vete" is Paty Cantú turning the tables on an ex who took her devotion for granted. She opens by admitting how far gone she was — "Creí que si te ibas el mundo acababa" ["I believed that if you left the world would end"] — before the chorus flips it into an order: "Vete, vete, vete de mi vida" ["Leave, leave, leave my life"], "Yo misma pinto la salida" ["I'll paint the exit myself"]. She sends him off with his own excuses — "Empaca tus mentiras" ["Pack up your lies"] — and lands on the line that gives the song its bite: "Soy la que perdona pero nunca olvida" ["I'm the one who forgives but never forgets"].