It shall come to pass, when Yahweh shall have done to my lord according to all the good that he has spoken concerning you, and shall have appointed you prince over Israel,
So Abigail is there pleading with David. Beautiful woman, has brought all of these things, and she is making good sense. "You know why should you avenge yourself. God will avenge you David. He's taken care of you, and so forgive the foolishness of this foolish man."