Sun is ruthless - remember The Glass Ballerina. I don't buy the whole, "I don't blame you." thing. I think she blames everyone involved with Jin's death. I think she is responsible for the lawyers whether it has anything to do with Kate running back to the island or not.
How better to get back at Kate than through Aaron? Sun asked her point blank what she was willing to do to protect her child.
I agree, I've always said don't underetimate the Asian chick!

Honestly, I'm surprised that it took this long for the real world to ask for a paternity test. You'd think that all the Oceanic 6 would have undergone some routine physical and psych check after the crash and the staged rescue. Instead of taking Kate's word for it they should've spotted right away that she had no claim on Aaron as her own child, so now she's left to do what she does best and RUN. Too bad she's legally not allowed to leave the state.
I do believe it is a ploy by either Widmore or Ben to somehow get her back to the island. Widmore, to find the island. Ben, in order to get her and Aaron back to the island. At this stage it might not matter who those people worked for because Kate and Aaron are both officially on the lam.
I am curious as to the fate of Ji Yeon. Since she was conceived on the island does that make her part of the Oceanic 6 and require Sun bringing Ji Yeon back to the island too?