I like the really minimalistic single-note piano that starts out the song--I think it’s unusual and effective and actually loses a bit of power once the chords come in (although it probably wouldn’t work all the way through without a break or rhythmic shift at some point). I like your melodies in general, and the chorus melody/chord progression in particular, although I’m not sure it works super well with the lyrics, that melody feels more like a love song than a breakup song. I do wish the lyrics played with the idea of the chupacabra a bit more than just naming it as a generic bloodsucker.