Missa my dear....
Self induced growth via orgasm:
Girl is underdeveloped for her age which has caused her to be less than popular with the boys, and on her 21st birthday she is home alone as usual, has a few drinks, sees a guy that she finds VERY attractive on the movie she is watching, something clicks inside here causing here to become aroused, and the magic begins, she must please herself and as she does her body begins to develop but she looses control and can't stop unless she climaxes.
I'm not a writer, I'm sure you can fill in the gaps, as you grow
