Disclaimer: I am not Rowling. The plot bunny bit me, that's all.
Moth to a Flame
She's always been attracted to him – like a moth to a flame. He is glorious and brilliant and perfect in everything he does. Next to him, any other man is outclassed, tarnished, boring. He is a bright-shining star in her night, but not a star. No, he is a bonfire, huger and brighter and more reachable than one of the stars, who shine small and distant in the night. She forgot the other thing about bonfires: They Burn. When she reaches out to touch him, she starts back with a cry, cradling a singed hand, but yet she returns.
Then they locked her away. In the dark, so so so many long years and he isn't coming and help she's terrified and cold and lonely without her beautiful bonfire. Finally, he rescues her. It has been half a lifetime, and she is no young strong beauty anymore, but she is still a moth, his moth, always his.
But now, she has forgotten. She is no longer clever and sly and nervous enough to snatch back her fingers from the all-consuming fire that he is. She remembers warmth, brilliance, light, and power, all she has missed. She forgets the danger. Like all the little moths flying towards a candle as if it were the sun's light, she flies, ever closer, fearless, drawn without consciously willing to go, straight into the fire...
She is a witch. Like moths, witches burn. Like everything else alive, witches die.
When we speak of being drawn to something, as a moth to a flame, we forget one thing. Moths always die in a flame.