One of the wonderful rituals to witness in our family is the tender intimacy between my wife and her 11-year-old when mum brushes daughter's hair while they're watching television together.
It is a moment when, despite all the other times of boundary-testing, that the back-chatty Tween becomes her mum's little girl again.
They chat about their day, about school, about the telly, but then the harmonious mood changes when the subject changes to...my stepdaughter's hair!
"You've got such lovely hair," my wife says, gently running a brush through the long blonde locks, bouncy and ringletty, as if they have been professionally styled.
"Stop it, Mum," says the SD.
"Stop what? You've got gorgeous hair. I wish I had hair like yours. Mine's so straight and boring."
Which is the strand that breaks the camel's back. The SD strops off, pulling at her fronds with her fingers, muttering something under her breath that goes along the lines of: "Why won't you let me have straighteners? It's so unfair."
To which my wife rolls her eyes and shrugs.
As a dedicated refusenik of fashion, I am frequently baffled by this repeated scenario.
"She's got lovely hair," I say to my wife, supportively.
"Why is she unhappy with it?"
"It's her age," my wife replies.
"She'll grow out of it."
But will she? It seems like more than that, to me. It's as if she just wants to look like everyone else. Bland.
She's started wearing make-up, too. Not every day, and certainly not to school, but for special occasions, like friends' parties. Just a touch of mascara, a smear of lipstick and a dab of blusher. But again, I'm baffled.
"Why do you want to put that rubbish on your face? You're naturally gorgeous as you are," I protest.
Her real dad says the same. But she's not interested in what we think.
"Because my friends wear make-up," she snarls.
"I'll stick out like a sore thumb if I don't."
"So?" I snarl back. "You'll be an individual instead of a sheep."
But she doesn't give a flock. She wants to belong to her peers. Her parents' perspective is pointlessly pathetic.
Of course, this isn't a new thing. Girls have always wanted to keep up with the Jenny Jones's in the fashion stakes, whether as tartan-clad Bay City Roller-girls in the 'Seventies to New Romantics in the 'Eighties to the Goths of the 'Nineties. It's wot's cool, innit?
But those fashions at least seemed to allow for individual interpretation of The Look. Today, young girls – even 11-year-olds like my stepdaughter - seem to aspire to just look the same as everyone else. Why is this?
According to new research, girls are under more pressure to conform than ever before.
Abigail Tazzyman, an academic at York University, who studies the grooming habits of women aged 18 to 25, explained: "Girls report a great hostility to anyone who doesn't look the same. The spectrum of what is acceptable is very small. It is not, for example, enough that girls must all have straight hair; they must use GHD hair straighteners."
Another academic to warn of the perils of increasing pressure to look good is American lecturer and film-maker, Jean Kilbourne, who documents how mass culture, including advertising and magazines, represents women.
"In the last 40 years, culture has stepped beyond setting an ideal image of beauty for women to aspire to: now it sets an impossible image," she said.
"Thanks to the spread of photoshopping, the flawless look teens seek to achieve simply doesn't exist in nature - with frightening consequences to self-esteem.
"This is not a trivial issue. It is not just about vanity. This takes up an enormous amount of psychic space. It depresses girls and has a drastic effect on self-esteem."
So where has this obsession with perfection come from? The answer is to be found, in part, in celebrity magazines where page after page shows glossy girls with perfect skin, bright nails and neatly applied make-up. As a result, girls are piling on the war paint at an increasingly young age.
Make-up artist Bobbi Brown said: "I used to reserve black eyeliner and a little bit of a smoky eye for 18-year-olds, but there are plenty of 15 and 16-year-old girls that wear it now."
Her views are confirmed by a Mintel report which showed that during the first decade of the 21st century, spending on beauty products by teenage girls shot up by 90 per cent.
"Teenage beauty standards are constantly shifting into more adult territory as girls want to be seen to be more mature at a younger age," it concluded.
Teachers too have expressed their shock at the modern make-up craze.
One told The Times: "There were 14-year-olds with perfectly established beauty routines.
"They all had tong-straightened hair, perfectly caramel-tanned skin and perfectly done nails. None of it was tasteless, except in that you may consider it tasteless that they had spent so much time on such a thing."
Cathy Cassidy, a former agony aunt for the teen magazine Shout added: "Diversity has been lost. There seems a desperate desire to conform and be accepted. Girls see from celebrity magazines that success is not measured by how many singles you've sold or how well your movies do at the box office. It all comes down to looks."
So what can we parents do about it?
The key, according to Steve Biddulph, author of Raising Girls, is to give our daughters confidence in themselves so that their self-esteem isn't derived from media and Facebook 'Likes'.
He said: "Help her find her spark - the idea that girls usually discover a passion or interest that really makes them excited and happy to be alive. Finding her spark - animals, hobbies, activism, sport, creativity - takes her away from being obsessed with how she looks.
"It's natural to HAVE self belief, but the media/fashion/advertising world takes it away, makes you not like yourself."
Good advice. Or alternatively, pull the plug on the computer and buy her a pony!