Sun has told two people (Widmore and Kate) that she wants to kill Ben.
On the one hand, Jeff Jensen at EW.com guesses that it might be a rouse of some sort. That she’s really working for Ben as a double agent, or possible that Sun is now involved with someone really powerful that wants to kill Ben – The Economist – and she’s protecting her new life?
I’m pretty sure that Jeff was joking about “The Economist”, but I think he’s on to something about protecting her “new life”. It’s not that she wants to protect some new man she’s with… It’s that she wants to protect the new girl she’s with – Her daughter!
After all, if Sun learned that Ben wanted to get them back on the island, that might mean that she would have to go without her daughter. Even with her daughter, I don’t think Sun would be to ready to go back. She’d do anything to protect her, and the best way she can think of is to kill Ben.