To keep her knowledge of the affair secret while she ruins Mark sexually.

As Cynthia explores the app and reads up on its functions, she formulates a plan. It won't be easy, especially since it'll take going home and acting like everything's fine, but she wants to humiliate Mark the way he did to her. She wants to make him feel as small as she did when she was standing in the hallway watching her husband pound her best friend on the same sheets Cynthia had picked out to match the room's curtains. And she wants to waste his time, the way that asshole had been wasting her time for the eight years she'd spent as his wife.

As she drove home, she practices how to act as to not let on that she knew. That alone should put her in the running for an Oscar, but she has to try. After parking her car outside her house, she takes out her phone. Sure enough, she's close enough in proximity to take control of Mark's cock. A thrill runs through her.