The Weregirl

For years Andrew has trained to become the person he wanted to be - the king of martial arts. He was well known, nobody didn't know his name. Girls and women fell for him when they could take a double take at the work visible as his upper body.
Andrew had a sister, Diana. Diana always played the support role in Andrews life. She cooked for him, kept their home clean and supported him on every way, especially mentally, since Andrew had a weak mind before his sister started to help him.
She was the intelligent one of them, visiting the near university studying chemistry and psychology.
But she developed a special envy - she didn't get any recognition for anything, even her brother didn't let her feel worthy for anything she ever did. He took it as granted, nothing special at all.
One day Andrew rub it too far. He didn't thank for the meals, complained about how messy the apartment would be and even shouted at his sister. Diana's inner rage took over. She knocked him down with one blow through his face and immediately binded his arms and legs on the floor. She brought a CD Player in and turned the lights off. "You will stay here on the ground for the next several hours. Your ignorance has to be punished. As well as I need a new test object. You need a drink?" She was cold. Diana went out, Andrew could see and hear that Diana was mixing up some sort of brew. "Drink this" She forced him to drink the red liquid and immediately sealed his mouth with a tape. His eyes were full of fear and he wasn't able to free himself. Diana started the CD Player. Strange sounds filled the room with a mysterious vibe, followed by a voice. Diana left the room and Andrew fell into a deep trance.
"Every time you see or even think about a girl or a woman, all her treats and her appearance will burn into your mind. And every time someone says anything positive to you, everything about the last woman will explode on your body and take over your mind and body. You are helpless to yourself and will not be able to stop anything about it. The more you resist, the more you think about that woman, no matter what age or appearance. You are addicted to the presence of woman and other people, if you try to resist, you will transform randomly into anything womanly possible."
The mixture Diana created enforced the hypnotic trance and strengthened the effect of the submission. She freed her brother and always followed him whereever he went, just to see the different kinds of explosive transformations. For her, it was like the blossom of the girl of every kind out of a rock. How the muscles disappeared, the breasts shooted out of Andrews/Annies chest, as well as the new girl nearly went insane to keep her desires peaceful.
The trouble Andrew caused wasn't bearable for Diana anymore though. She decided to keep him/her at home, chaining him in his room. Every now and then she comes into his room to feed his addiction with her presence and to say him "very well done, my beloved sister" as he turns into his sister to go wild on herself.