GLOW

She had a poisonous mind. One that turned off all the lights inside so only the darkness remained. She was raised as such, taught to never speak to devils, though she bowed to them and begged for a mercy none could bestow.
Then she met you. The light in her flickered slowly, skeptically. Before long she was beaming, from the inside out. She had never known herself, or the capability of light within her, not until the day you flipped the switch.
But even the brightest spark will come to pass, even the most beautiful glow would not entrance you forever. And she would learn once more of the damp within the darkness, the very day you walked away.
She still flickers from time to time. And while she does not know of her power, occasionally she will illuminate. She will glow. And you will see her shine, albeit far from the home she built you. And you will miss the heat of her blaze as you realise all you took for granted.