She's just entered that notoriously difficult decade for women - her 50s - when it's so common to find confidence wilting and style looking old hat.
And, of course, it's usually at this moment women's waistlines begin the great middle-aged spread.
So what on earth is the Countess of Wessex's secret? At 51, she looks sleeker, more glamorous and more youthful than she has done for more than a decade, the Daily Mail reports.
Indeed, an appearance at the New Forest and Hampshire County Show this week saw a radiant Sophie looking trim in an elegant Prada brown and cream dress, with a crisp white cardigan.
So how is Sophie seemingly managing to age backwards?
Well, it has lot to do with the loyal male dresser whose tasks include zipping up her dresses, a fiendishly organised inventory of each and every item of her clothing, and a high-tech £1,000 bike.
All have contributed to her glossy transformation - as has her careful courting of the Duchess of Cambridge's favourite fashion designers.
Boring Sloane is now a fashionista
The Sophie from the days before her 1999 wedding to Prince Edward is virtually unrecognisable compared to the sleek creature we see today.
Back then, she stuck to an underwhelming mix of corporate wear, fitting for only the most frumpy of Sloanes.
Boxy newsreader jackets, big shoulder pads that dwarfed her frame and sensible shoes - with occasional forays into pastel fussiness and sequins - were the order of the day.
One cruel sort even said, on her engagement, that she dressed like a Bulgarian flight attendant.
But look at Sophie now: so confident in her own impeccable style that she's even become patron of the London College of Fashion.
Her whole silhouette has changed, too. When once she concealed her figure, today she picks clothes to emphasise her nipped-in waist.
And, like Kate, Camilla and the Queen, she's woken up to the importance of made-to-measure.
And that's not the only area where Kate has been an inspiration. Indeed, Sophie's favourite designers these days just happen to be Kate's favourites, too.
She loves Emilia Wickstead, the young New Zealand-born Londoner who specialises in Grace Kelly-esque ladylike dressing; Roland Mouret, the Frenchman who knows how to flatter every inch of a woman's body; and Erdem, who is also beloved by Michelle Obama.
There have also been some very Kate-like Alexander McQueen coat-dresses, alongside Catherine Walker, famously favoured by Princess Diana.
Sparkling in tiara and glam jewels
Dress fittings take place at the Wessex apartment at Buckingham Palace amid much chatter. Sophie is a perfectionist - everything she wears has weighted hems to protect against sudden gusts of wind.
Sophie's favourite hatmaker is Jane Taylor, who knows exactly what suits her - smallish numbers, placed on the side of the head.
Her shoes, too, are higher than they were, and are often leg-lengtheningly pale (rather like Kate's oft-seen nude heels).
But unlike Kate, who prefers tiny jewels, Sophie loves all kinds of gems. Like the Queen, she often wears a brooch, and she's not afraid of a tiara or wearing big sets of rocks for evening engagements.
And she has a collection of ladylike watches, from Cartier to Rolex.
Male dresser keeps her looking stylish
Sophie, ever the canny PR girl, is not one to have a stylist. Who wants to look as if they can't choose their own clothes?
But what she does have is a dresser. David 'Quicky' Quick, 51, was Sophie's deputy butler and cook, but has somehow morphed into the person who keeps her wardrobe as meticulously well run as the Queen's.
Ever capable, he's like Downton's butler Carson, always exuding an air of calm. Like Sophie, he has an eye for detail. He's smiley, courteous and trusted.
So what does a dresser do? Well, apart from pressing her clothes and laying them out, royal sources say he is often in the room when the Countess is dressing for a special occasion, and might even zip up her dress and help her on with her jewellery.
Quicky, who has served his mistress for more than a decade, always goes the extra mile.
He maintains Sophie's extra- ordinary computerised wardrobe inventory, where her clothes are colour coded, labelled, photographed and indexed by computer 'so she can see what she wore with what, when and where, and with what jewellery,' says an insider.
As well as being hand-pressed, all Sophie's clothes are treated with organic washing products, steamers and a lot of starch, linen and fabric spray.
The ferocious attention to detail doesn't stop there. Shoes, leather handbags and jewelled clutch purses are photographed for reference, cleaned, bagged and tagged.
Hats are stored in non-acetate tissue, each milliner's box labelled and stored away from heat. Dressing rooms and wardrobes are kept cool and locked.
Luckily, Sophie's home, Bagshot Park in Surrey, is a 50-room whopper, so there's plenty of space for walk-in wardrobes.
Sophie adores Quicky and his organised touch so much that he's received two honours: an RVM, or a Royal Victorian Medal, followed by an MVO, or a Member of the Royal Victorian Order.
She gets on her £1,000 hi-tech bike
If ever there was a good advert for losing a few pounds, it's Sophie. She's the trimmest she's ever been at a size eight, having dropped two dress sizes since last year.
How? A gruelling fitness regime. She swims, goes to Pilates classes with other school mothers, works out on her cross-trainer at home and runs three miles twice a week, sometimes with Edward, round the 52-acre grounds of their home, always in her favourite Asics trainers.
That would be enough for most of us. But not Sophie - she's also cycling like mad.
She's even completed training at the Royal Military Academy and will take part in a long-distance cycle challenge in September to mark the diamond anniversary of the Duke of Edinburgh award scheme.
On her rather swish £999.99 carbon lightweight bicycle with 20 gears, designed by Olympic cyclist Chris Boardman, she will cycle with others from Holyrood, Edinburgh, to Buckingham Palace, a distance of 445 miles over seven days. It's quite a challenge.
'Army personal trainers keep Sophie in peak fitness as she prepares. Though, having endured years of back pain, she also knows when to rest,' says a source.
'And during the summer holiday at Balmoral with her family, she'll be racing about on two wheels, whatever the weather.'
She also skis. With Edward and their two children, Lady Louise, 12, and James, Viscount Severn, eight, she was in St Moritz earlier in the year on their annual ski trip.
And she rides with her children, as well as often with the Queen.
All in all, she's lost more than a stone since her less active days.
Blonder, longer hair - and a tan
Her beauty regime is relatively low maintenance - apart from her hair colour.
An aficionado of Richard Ward's Chelsea salon long before the patronage of Kate, Pippa and Carole Middleton came to light, Sophie has delicate blonde highlights and lowlights.
As the years have passed, she's become blonder and blonder.
Her cut has changed, too. The severe bob of old has given way to softer, layered, longer hair - in contrast to most women, who chop their hair short as they get older.
As for hairstyles, Sophie favours pretty chignons or, as seen this week, a ponytail she does herself.
She's also managed to row back the years by embracing a light tan - indeed, she loves the sun and often has freckles - and favours a light 'no make-up make-up' look, which she does herself.
No ageing Kate-style black kohl around the eyes for Sophie.
Minimal cosmetics include Japanese brand Shu Uemera's Face Architect Exquisite Satin foundation.
She likes serums that leave her skin oil-free, such as Crystal Clear 'No Shine' Serum. Make-up includes Chanel Rouge Allure and Rouge Coco lipstick.
As well as being flattering, her make-up style is highly practical, as she hates having to touch up her face during royal engagements.
Sophie has never smoked (she loathes it) and so has preserved an almost perfect complexion.
Her teeth are well kept, but unlike Kate, she has avoided Hollywood-style veneers. However, she does have regular French manicures, foot spas and pedicures.
Content in her royal career
Her happy glow is partly down to the fact she feels more secure within The Firm than ever before.
After the humiliation of the News of the World 'Fake Sheikh' sting in 2002 - when she made a number of highly indiscreet comments to an undercover reporter - Sophie gave up her PR business and Edward gave up his TV company, too.
They came to accept that commercial activity and royalty just doesn't mix; one reason, perhaps, they have decided their children will not be brought up royal, but will work for a living.
In the meantime, both have embraced charity work, which Sophie adores.
She's president of more than 70 charities, many concerned with children with disabilities or communication problems.
She and Edward often represent the Queen abroad, such as at the weddings of foreign royals or in the Commonwealth.
And last year she did 169 UK engagements and 49 abroad, placing her way ahead of William, Kate and Harry.
It's all impressive given that she's often does the school run and is a hands-on mother.
Near tragedy changed her life
At the start of her married life, Sophie had a more laissez-faire attitude to her diet. That all changed after an ectopic pregnancy in 2001 when she became health conscious.
Then, in 2003, while pregnant with Lady Louise, she began to haemorrhage at Bagshot Park. Alone, as Edward was away with the Queen, she was airlifted to nearby Frimley Park hospital semi-conscious.
She was later said to have been 15 minutes from death. 'She doesn't like to talk about it and can't remember most of it,' says a source.
Louise was born a month early weighing less than 5lb and went straight to intensive care. Sophie lost nine pints of blood and spent 15 days in hospital. The experience sparked a lifestyle overhaul.
Today, she eats well: no crash diets, just healthy organic food. No bread, fried food, sugary puddings or pastries and very little alcohol.
Smoothies, porridge, chicken, fish, salads and vegetables are on the menu, instead. Clearly, she has tremendous self-discipline.
Style tips from the fond Queen
Sophie is particularly close to the Queen. Indeed, the monarch has become her mentor, especially since the death of her own mother, Mary, in 2005.
Sophie tries to emulate the Queen's way of making everyone who speaks to her feel special and, as she has said, to 'do things in a slightly more elegant way'.
Indeed, there are similarities between Sophie's new stylish wardrobes and the Queen's - a liking for bright primary colours, neat 'regal' tailoring and eye-catching jewellery.
The Queen is said to be immensely fond of her, and the pair have a shared loved of military history and can be found poring over the archives together at Windsor Castle.
Saturday mornings are often spent riding together, and both have horses at the castle, 11 miles from Bagshot.
The glow of married bliss
Edward is the only one of the Queen's children to have stayed married. Louise being born in such dramatic circumstances is said to have made him realise just how much his family needs him.
He rose to the challenge and 'Sophie has always been able to rely on him', says one close to them.
While she is organised, caring and ensures the children do their homework, Edward is playful. 'Once he was petulant, but fatherhood totally changed him. He's very considerate. When they play raucous games of hide and seek, the children scream with laughter.'
Edward delighted in feeding them as babies and played horsey with them in their huge nursery on the first floor of Bagshot. 'Sophie, meanwhile, is the one who makes everything run like clockwork.'
But despite their differences, they are united on how to bring up their children - with virtually no TV and lots of fresh air, taking walks with the two family dogs.
Recently, Edward has become green-fingered, aided by Sophie, and together they have created a new woodland garden at Bagshot.
'Horticulture is their joint passion,' says a source. 'They are very happy.' And, looking at Sophie's smile this week, can't you just tell?