part of what makes us human is our sense of identity and our ability to have strong feelings towards things. Terra's whole side of the story is coming to grips with that identity. As well, Terra was not part magic, she was part esper, and although espers were magical beings, her body itself was not that of an esper's (till she morphed anyways) so it doesn't really make sense for her to disapear physically from the world.
Let Terra Live! :P Shes my all-around favorite character.
