Atravesar literally means "to cross" or "to go through," but it can also mean "to pierce" or "to run through something."
In this song, the singer uses it in a more metaphorical and emotional sense: "Por si me vuelves a atravesar" (In case you pierce me again). It suggests a deep emotional wound or pain caused by the person, implying that their presence or actions have hurt her deeply in the past and she fears it happening again. This makes it a compelling and emotionally charged word.
Have you ever felt completely captivated by someone who doesn't even know you exist? Nena Daconte's "Al Son De Una Guitarra" explores this powerful and painful feeling. The singer describes an obsession that "barely lets me sleep" for someone she feels she has "nothing to do with." It's a one-sided fascination that makes her feel small and insignificant, like a single "leaf" you can simply "watch fall."
The song paints a vivid picture of feeling paralyzed by an unrequited crush. The object of her affection seems magical, surrounded by "the flight of the butterflies," while the singer feels her own identity fading away. She admits she's forgotten how to be her joyful self, to "jump, run, toast, make myself shine." Her voice is "half-frozen," silenced by this overwhelming and unspoken love.