Everything about Edea is deeply creepy, but that's part of why she's one of my favorite characters. Her apperance, her theme music, her story arc, and even the faint sounds of bells when she appears in combat are all very cool.

But anything related to Sorceresses in the game are intended to be creepy. It would explain the persecution and apparent revulsion that Ultimecia and other Sorceresses endured.

I'm guessing the translators chose to use sorceress instead of witch because there are more negative associations with the latter, at least in western cultures. But the creators clearly intended it to be witch, as the hidden anagram in the song you mentioned demonstrates.