It means she's from somewhere else. Andi, "she is elsewhere/somewhere else" would be "elle est ailleurs"

I don't know the song, but it means "she is elsewhere/somewhere else." That's the literal translation, at least. If there's some deep poetic meaning, you'll have to wait for another answerer:)

Nacir, maybe you'll also like "elle se balance" by Tcheky Karyo, the voice and the style are similar but this song is more recent. http://www.youtube.com/watch?v=xfgx5LeZgUU