Saul said to David, Behold, my elder daughter Merab, her will I give you as wife: only be valiant for me, and fight Yahweh's battles. For Saul said, Don't let my hand be on him, but let the hand of the Philistines be on him.
So I don't know what kind of a daughter she was. I don't know but he figured she'd be a snare to David and give him problems, which she did in time.