I've been thinking that, too. But then how can everybody else see her and converse with her? And what purpose would the island have for keeping her "alive" then? Maybe to bring Aaron into the jungle for Christian Shepard to take...
What about Rose's comment, too? That the island heals, so why is Jack getting sick? I'm still pondering that one...
$100 bucks says Jin dies in the season finale. I stole this from the EW recap, but: maybe the redhead freighter girl (Charlotte, I think) has some connection with Sun's dad, Mr. Paik. I mean, she speaks Korean? I think that Mr. Paik might be more involved a la Chalres Widmore than we've seen so far...