Vanessa sees your blow coming and dodges it, getting a few chairs and people between the two of you. Before she can retaliate, a group of Stormwind officers arrive. Their leader announces, "Vanessa VanCleef, you are under arrest." Vanessa looks scornful. You can see her eyes darting from one to another, plotting how to take them all on at once. But in the time it takes her to do that, they have her disarmed and bound. She has no choice but to comply. Once things have quieted down, you're left with a few options:
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.