I hope this puts you in a Halloween mood. I hope it wasn't too horrid. It felt fairly true to the Marianne who got deathly sick after W jilted her.
And if you want a happier ending, the ending I tried to write first splits off right before Nelly offers to kill Marianne.
Basically, Brandon notices the maid and asks who she is. Nelly reveals herself to be a devil who will own Marianne's soul after her 10th failed wish. Marianne is horrified to find this out but Brandon offers his soul in exchange. He's older, he reasons, and Marianne doesn't deserve such a fate. They argue and (writing magic) somehow the end result is that they each end up with only half of a soul -- not sure if they share a soul or what -- but they end up together because the only way they feel at peace is when their half souls are united.
