Nothing about the kind of magic Dumbledore was using made the least bit of sense. Used to being able to feel magic and use it intuitively, what he required from her went against everything she had ever been taught. Not only was she stripped of the wand that she'd been using for longer than she could remember, she had to consciously think about her actions before she made them. In the past, she was able to just let the magic run freely from her body and out of the tip of her wand. She never had to worry that it wouldn't work when she needed it to. It always did.