You don't have to say much. Whatever you manage to get out about Vanessa's status, it's enough. The crowd rises against her. Before she can act against them, she's been swept out of the room. You never see her again.
Use your new power to conquer Westfall once and for all. Use the downfall of the Defias to align Moonbrook with Stormwind again. Remain neutral. Just keep your hold on the town.