Susan saw that he flinched at the very last minute, and only just hit his elbow with the curse, but now he was aiming at her. She quickly ducked out of the way of a quickly cast slashing curse, that only managed to chop off some of her hair.
Another spell flew quickly from her wand. The first spell that fell from her lips was lame, and she knew it, but 'Furnunculus' could be nasty, and she aimed it directly at his chest.