I may be wrong but I really don't think there's enough of a continuous history of attestations to have the female name Tempy/Kempy in the song descend from the ME Kemp-name forms; they do sound masculine, too. I don't doubt that either Kempy or Tempy could be a name, but I would like to know more.

Usually words are corrupted in transmission into an easier or recognizable form (and there's no shortage of two syllable female names that end in -y). So it's intriguing to have what seems to be an obscure form here.