While fighting Madamme Amberly, Cortex will have unlimited ammunition. Avoid the electric beams from Amberly. You can see her aiming point when you are seeing small flames coming from the platform. When she hits it, it will expand and close it by shooting at it rapidly. After that, she will shoot school bells slowly to you. Shoot them all rapidly. After that, when Amberly turns around shoot at her engine. Repeat this a few times to defeat her.