This was taken from a poster on ABC.com/Lost named reallyReneee
Jacob and MIB's "mother" spent the whole episode building up to her replacement. Were lead to think she has chosen Jacob to replace her duties of protecting the island. But what if she actually chose MIB to replace her job as...wait for it...THE SMOKE MONSTER! The whole episode is about her manipulation on Jacob that eventually leads him to throw his brother into the light which turns him into the new smoke monster.
She left the game on the beach to start a rivalry between the two boys. She used her "smokey" powers to appear as MIB's real mother and guide him to the others. She saw that MIB had all the qualities to be the evil smoke monster (able to lie.. ect.). What kind of woman beats a pregnant woman with a rock and steals her babies? an evil woman! a smoke monster! How did she ruin the camp and destroy the well in such a short amount of time...well, if she turned into smokey then poof! easy! She told Jacob the light was a fate worse than death. hmm..sounds like she knows from experience! She knew MIB would kill her, so she showed Jacob exactly how to get his revenge on MIB, throw him into the light! Which made MIB her replacement, which was the plan all along! Jacob was only a pawn! And just like the surprise dagger in the back ultimately killed her, you may recall Dogen giving Sayid the dagger to go kill fake locke, but he didn't manage to catch him off guard.