Hello,
In the story I'm thinking about Kayla Biggs is a regular girl next store woman who decides to join the big time, and pursues a change to her life. Her boyfriend helps nudge her down the path of bigg-iggness!
Kayla was soon thinking about how she can grow larger and maybe get into modeling, or showing off her growing physique.
You could be her plastic surgeon boyfriend, a geeky geneticist, or even a closeted magician who is trying to make Kayla the biggest girl in the world, or that has ever lived.

Anyways, I think it would be a fun concept to explore, please message me if you are interested.