Before and after: Bristol Palin photographed in 2010 (left) and earlier this month, following her surgery (right). (Gregg DeGuire/Jimi Celeste/Associated Press)

In the musical “Gypsy,” about a stage mother so famously domineering that she drives her daughter to become Gypsy Rose Lee, the most famous stripper in the first half of the 20th century, there is a pivotal scene in the middle of the second act. Strapped for fame and cash, human steamroller Mama Rose has signed up her daughter Louise to perform a striptease. And as Louise performs, cautiously stripping off a single glove, she starts to enjoy it.

Suddenly, Louise is no longer doing it to please her mother. She’s doing it to satisfy her own craving. It’s the tipping point, when the Dreams of the Mother turn into the Reality of the Daughter.

I keep thinking about “Gypsy” whenever I hear from Bristol Palin these days. Like Baby Louise, she’s the gawky, slightly awkward, normal-seeming American adolescent, suddenly shoved on the national stage without a natural performer’s bone in her body. And that’s a compliment. That was her whole charm. She was just Bristol — Bristol, whose motto until now could have been I Didn’t Ask For Any Of This.

Who cared how much money she made speaking about abstinence? We knew this wasn’t her fault. Sure, her erstwhile fiance and baby-daddy Levi was a transparent publicity hound, appearing as a “Playgirl” centerfold with a tactfully placed glove, or in music videos, or on the arm of Kathy Griffith or trying to run for Mayor of Wasilla. Deer in the Headlights? Please — more like Deer in the Self-Imposed Spotlight. But Bristol was disarmingly normal. When she made cameos on scripted TV shows, she delivered her lines in a Christopher-Walkenesque non-comprehending monotone, as though they were printed on a billboard slightly too far away for her to read with comfort. During her stint on “Dancing With the Stars,” we really believed that she was just a shy girl from Wasilla with a stage mother problem. She showed up on Sarah Palin’s Alaska and gamely clubbed halibut, and you could just feel her willingness to please radiating from the screen.

But something’s changed lately.

First, the book. Then, the announcement of another reality tv show on the Bio Channel, where she moves in with Kyle Massey of “Dancing With The Stars” fame and his even less mildly famous brother. Now, the dental surgery that magically had all the results of cosmetic surgery.

This is turning into an interesting second act.

Bristol, I’m concerned!

She’s becoming one of those peculiar aquarium fish, for whom the transparent glass seems as essential as the water.

It’s hard to blame her. The sense that someone’s watching is almost reassuring. When it comes to the Basic Requirements for Modern Life, attention ranks above shelter and food and just below water. Perhaps we were wrong. Perhaps this wasn’t What Sarah Wanted. Perhaps this is just What We All Thought We Wanted.

But she’s losing her appeal. We liked her because, well, it wasn’t her fault. She was that unicorn-like rarity: the reality star whose pretense of not seeking celebrity rang true. Some people are born reality-TV stars (Gosselin children), some achieve reality-TV stardom (Kardashians), some have reality-TV stardom thrust upon them! And that last category belonged to Bristol — until now.

Maybe there was never any way to stop it. As Louise learned, you take off the glove for Mama, but the crowd roars for you — and then, well, you can’t just go home to Wasilla. Not anymore.