A lot depends on the information Sun gets from Locke after he visits them.
I kind of think that Widmore is the other person besides Paik that Sun holds responsible for Jin's "death", or their separation, since it was his search and destroy mission that brought on the mercs. That would make the coy merger that she's doing with him all the more poetic in application, in the vein of "keeping your enemies closer", before she destroys him financially or whatever. Or, Locke could use the info of why the freighter blew up to get Sun mad enough to go back and do whatever it is that Locke needs them to do. But if she finds out about what happened in the Orchid, she could go after Ben off-island instead. Then the path of vengeance-begetting-vengeance becomes the theme of her sad future too -- that is, with Ben killing Keamy and blowing up the freighter to avenge Alex, then Sayid killing to avenge Nadia, Sun killing Ben to avenge Jin, and who knows what else in Seasons 5 and 6. (Quite frankly I hope that all the killing on this show starts to wind down soon!)
Hopefully Sun merely wants to mentally and financially twist the b@lls of the guys who are responsible for separating her from Jin (like the coup of her father's business, rather than killing him) and doesn't end up lowering herself to committing murder like those she feels are responsible. Even though she defended herself well against Colleen on the sailboat (most likely due to being pregnant making her even more defensive), up to this point I don't think that Sun is a killer per se, but you never know with this show. Most of the characters are turning tail on their own personalities, for good and bad and crazy, ever since they got to the island.