Saul said, I will give her to him, that she may be a snare to him, and that the hand of the Philistines may be against him. Therefore Saul said to David, You shall this day be my son-in-law a second time.
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.