To "prick one's heart" means to reveal to someone the full extent of how their words or actions have negatively affected others, and also how those same words or actions are displeasing to God. Since the Bentleys had taken vows before God to be faithful to each other for the rest of their lives, her last hope was that God would remind Governor Bentley of the promises he made to her, and to God. It's like when you hear that God "convicted" someone to do X or not to do Y. It's the belief that