Even after she had him dig his grave, but then said, "Not today, love."
She made certain that he went back to that spot in the woods and kept his gravesite tidy and ready to use. After all the false executions and the partial-living burials she'd done to him, he'd come to cease believing that she would ever really kill him.
That's when she did, and the shock when he knew he was about to die was priceless.
He'd become ready and reconciled and prepared to face his death, but then she let him hope again, and believe that maybe she loved him enough to keep him.
So when she killed him, the fear and the shock and the pain of betrayal in his face as he died was so delicious.