Exploited: A con artist takes advantage of her desperation and sells her an expensive scam treatment.
Defied: "I'm not stepping into the Gender Bending machine. I just know it'll break down immediately, and then I'll be stuck as a girl until it gets fixed, which could take months if I'm lucky, and could very well be permanent."
Discussed: "He's a girl now, huh? Ten bucks says he never changes back."
Conversed: "Why is it that any character who is turned into a girl for more than five minutes stays that way?"
The newgirl goes through severe bouts of depression as she slowly loses hope of ever returning to her old life. After a lot of soul searching, her friends reminding her that she's still herself inside, and not a small amount of therapy, the new girl comes to terms with her new lot in life.
The ruins of a civilization were found where Gender-Bending magic which followed this law was used. It's revealed that the civilization fell after the gender ratio became skewed to the point where the remaining males simply couldn't keep the population levels up. Or, in case of male genre being the thriving one, civilization fell because the remaining females couldn't keep the population level up. The civilization continued using the magic even when it was clear that too few children were born to continue the practice.
Desperate to turn back, the transformee undergoes transition.
Feeling too humiliated to live as a female, she becomes a recluse.
Reconstructed: The newgirl comes to terms with her new lot in life after a lot of soul searching, only to rededicate herself to finding a cure. In the meantime, she decides to live out her life as best she can.
Played For Drama:
His transformation to female rewrote his DNA so that instead of a Y chromosome, he had another copy of his pre-existing X-chromosone... With no Y chromosome left, transforming back into a man means somehow making one from his second X chromosome and even if that was a success he wouldn't be the man he was before. He'll be even further from where he started. Disgusted and disappointed by the unrecognizable man in the mirror, he goes back to being a woman... It's as close to who he was as he can get.
Alternatively, driven to despair by the fact that he will never be able to be himself ever again, he takes his own life.