You realize that you need to get the gun away from her, but how? If only you could get up there --
And suddenly you are! That's right, you can fly! You forgot. You're hovering next to the fire escape, she looks at you in terror, and you quickly punch the gun up and out of her hand.
Whoops, you forgot about your strength, too. The gun flies up, and up, and up, and you watch until it disappears into the cloudy sky.
"You fool!" shrieks Genius Woman, and you look back at her. She keeps yelling at you for some reason. "The main circuitry in that gun is inside a chamber that's designed to be under pressure from the atmosphere! If you punched it high enough, it'll rupture due to the lack of atmosphere! And then it'll be like the gun is firing, forever -- or at least while it's getting solar power! The effect will be widespread, depending on how high the thing ends up! The only good news is that it should stop once it comes back down and hits the ground! Do you understand what I'm telling you?!"
"Huh?" you ask.
"Do something!" she commands. She points skyward. "Fly up and intercept the thing before it turns everyone in a 20-mile radius look like me! Or, hell, use your stupid wishing power to fix it! Why not?"
Something dimly gets through to you, as Genius Woman begins muttering something about being glad she still has her intelligence.