JACK: Why are you here?
BEN: I'm here to tell you that the island won't let you come alone. All of you have to go back.
JACK: (Scoffs) Are you... (sighs) Sayid--I don't even know where Sayid is. Hurley... (scoffs) is insane. Sun blames me for... and then Kate... (chuckles, sighs) She won't even talk to me anymore.
BEN: Perhaps I can help you with that. This is the way it has to be, Jack. It's the only way. You have to do it together, all of you.
BEN: I have a few ideas.
(Jack sighs deeply and turns to leave.)
BEN: Jack... I said, all of you. We're gonna have to bring him, too.
So, I think it is part of Ben's plans to unsettel her, get her on the run where she has no where else to go.