I don't know who the second person is that Sun is blaming for the death. From the look of the season finale I'd say that it's Jack (from the comment Jack makes) but if she could somehow find out that it was Ben that caused the explosion that would explain her alignment with Widmore. I wonder if she blames Jack for something else. He never finishes his sentence and it would have been very easy to just say that she blames him for Jin's death. Maybe they are misleading us...again.