Disfracé is the past tense of the verb disfrazar, which means "to disguise" or "to dress up in a costume." Its noun form, un disfraz, is the Spanish word for a costume, like one you'd wear for Halloween.
In this emotional song, however, the meaning is purely metaphorical. Ela Taubert sings, "negué la realidad... La disfracé" (I denied reality... I disguised it), expressing how she intentionally ignored red flags and pretended things were okay. It's a poetic and memorable word to describe the painful act of self-deception.
Have you ever looked back on a relationship and just thought, "What was I doing?" That's the whole mood of this song by Colombian artist Ela Taubert. She's kicking herself for staying too long with someone who clearly wasn't worth it. She sings about realizing she fell for a version of a person that "nunca existió" [never existed] and that the real pain was that she knew the truth all along but chose to ignore it.
She gets so specific about the one-sided effort, wondering if the person even read the letters she wrote. The song's big, frustrating question is right in the title: "¿por qué no me fui antes?" [why didn't I leave sooner?]. It's that feeling of anger at yourself when you finally see things clearly and realize the other person never really cared. She nails the feeling with the line, "Decir te amo no es amar, estar a medias no es estar" [Saying I love you isn't loving, being halfway there isn't being there].