One of the most memorably bad concepts/backstories I have ever come upon is one of my favorite stories to tell.
I had been running a Vampire: The Masquerade LARP for about a year, and whenever I recruited new players, I tried to instill upon them how important it was to have an in depth concept for their character. It drives both the drama and investment for your gaming experience. I met a new player named John, and gave him my usual spiel. He got super excited and said he had an idea, but wanted to time work on it. He said he would get back to me in two weeks.
Two weeks pass, and he has sent me numerous emails about how pumped he was about his concept. He had been brewing it for two weeks now, and he knew I would be really into it. It was the best thing he had ever come up with.
Finally, we sit down on game night to make the character. I tell him to pitch the concept, and by now, I am really intrigued by his enthusiasm. He smiles, slaps his hand down on the table and says "German. Brujah." I wait for more, he just sits there.
That was his entire concept.
I should note for the none Vampire savvy out there, Brujah is simply a clan of Vampires. It would be akin to someone in Pathfinder saying their concept was a fighter. It is also important to mention he was not trolling me, and was completely sincere.
I have read both the basic rules pdf and have purchased and perused the starter box, and I for one am not immediately impressed. The rules still feel very 3rd edition, plus and minus a few things along the way. I do realize it is very early to make too much of a judgement. I am also not much of a rules based player or game master (definitely role over roll), and what I disliked most about 4th was that it seemed to be extremely fluff-lite. I really hope 5th does a better job with this. Paizo nails it.
After thinking about it, I concluded that I fell in love with D&D during 3-3.5, and during that time Paizo had a lot of influence (Dragon and Dungeon magazines, artists etc). When Wizards (Hasbro) made its decision to alienate them, I found myself again at Paizo's door when Pathfinder was released. Consistently great products with heart behind them. I may play in someone else's 5th ed game someday, but I believe my money is still going to Paizo.
All this aboleth talk made me think: what about an Azlantians Revisited book? Fill it full of stuff on the original Azlanti as well as their descendants: the gillmen, dark folk, morlocks, grimlocks, and mongrelmen.
Oooh...Azlantians Revisited...shut up and take my money!
I think it is rather unfair to judge this GM on one simple post. I agree, it does sound a bit heavy handed, but I took it as a rough idea for a personal development quest. It doesn't sound as if he plans to "punish" the character unless she chooses not to take part in the scenario (and I do agree that with some of the mature themes present, that it is something that should be talked about with the player first). I don't agree with punitive storytelling or game mastering, but still I think much of this thread has been rather insulting instead of answering a question.
Perhaps you could reward the character with a higher rank within the church, a new NPC cohort, or the opportunity to stop the slavers and therefore become a hero in the eyes of many?