Madame Masque was not so distracted by Castle as he was by her (and the musk of sweat, body odor and gunpowder that clung to him was not remotely appealing). She was ready for his counter attack and when she landed from the flip, it was on her feet, the knife still in her hand. Though it didn't stay there for long. She flung it as hard as she could, aiming for his chest. It lodged in his shoulder, dammit. Oh well, she'd be more accurate with a bullet.
Distant sirens wailed as she pulled her gun- Of course cops would be coming and firetrucks with that blown up building feet away. The sound of approaching authorities gave her a moment's hesitation that she would probably regret. Before she could waste another moment she aimed and pulled the trigger.