Here's some useful fashion advice from British pop star Pixie Lott: Don't wear the wrong bra with a white dress.

But if like her, you were stuck at Topshop on Wednesday night with no other options, throw on a cool, luminous yellow leather jacket to hide your fashion faux pas.

Lott, 21, was at the UK high street fashion label's outlet at Knightsbridge to play stylist to two lucky fans picked by local radio station 91.3FM through an online contest which invited participants to submit their worst fashion disaster.

She was in town for a showcase at nightspot Zirca last night where she performed hits like Mama Do and Dancing On My Own and did an autograph session at Bugis Junction mall on Thursday.

Nur Nadirah Umar, a 15-year-old student from Dunman Secondary School, won the competition with an ensemble consisting of a yellow top underneath a white and blue striped collared shirt, with blue jeans.

On Wednesday night, Nadirah and her best friend Shehzahdi Shehrin Boorhanuddin Moonshi, also 15, were at Topshop with their idol to pick out tops, dresses, skirts and skinny jeans in the bright pinks, florals and mint greens of spring.

But Lott - who "loves fashion - which girl doesn't?" - was also keen on going through a rack of clothes picked out for her by Topshop's in-house stylists.

When she finally put together her self-styled look of a flowing white dress with a babydoll waist and the yellow jacket, she admitted sheepishly: "I would (wear the dress without a jacket) but I'm wearing the wrong colour bra."

Lott recently ended a four-collection partnership with UK brand Lipsy, designing, among other things, dresses, playsuits and waistcoats.

So what makes her suited for the stylist role?

The always well-dressed Lott doesn't really rely on a stylist on a day-to-day basis - though she has one who helps pick out clothes for events - and she plays stylist to her friends back home.

"They always wear all of my clothes, and we go shopping together, and I help them pick stuff out," said Lott, who describes her personal style as "casual, with a little bit of quirk".

Sporting a charming but not too matchy-matchy combination of a Tory Burch blouse under a blue sweater, blue American Apparel shorts and a pair of flats from Marc Jacobs, she certainly didn't make any fashion mistakes for her "clients" Nadirah and Shehzahdi.

The trio, hounded by other Lott fans, spent about 15 minutes at Topshop.

Assisted by Topshop stylist Alyssa Sulaiman and personal shoppers Melanie Mak and Nadirah Abdullah, the trio looked at sleeveless floral tops while Lott discussed with the girls what kind of clothes they were looking for.

The teens each received Topshop gift cards worth $500, as did Lott herself, but they did not immediately buy the clothes they had tried on.

Lott's fans - known as Crazy Cats - stood behind a cordon, shouted the singer-songwriter's name, and went into a tizzy when she looked up and raised two bent fingers from each hand to mimic kitty ears.

Catty jokes

While the girls tried out Lott's picks, she chatted with 91.3FM DJs Boy Thunder and Charmaine Yee on everything from the schools they attended to her accessories and what to say to folks in Beijing when she gets there later this week.

Lott ribbed Yee on her first name sounding like a Chinese dish - chicken chow mein - and the toilet paper brand Charmin in the US and the UK.

Always on the prowl for a good cat joke, Lott pounced on the Malay word 'mahu' - she pronounced it "mao" - when being taught by Boy Thunder the phrase "Saya mahu makan" (I want to eat).

"So many catty words!" she said, laughing.

When The New Paper got some time with her, she spoke of her wardrobe essentials: Black dresses, red carpet-ready dresses, shorts, leather jackets.

"I've always got to bring a black dress and a red carpet dress on tour, just in case I have to go for a nice dinner or for an event," she said.

"And I always need a leather jacket, for warmth."

But fashion must have been furthest from her mind when she walked out - without shoes - to sign autographs for fans who'd been waiting outside the room.

Nadirah and Shehzahdi also eventually came out of the dressing room in the outfits handpicked by Lott - a floral top and pink jeans for Nadirah, and a pink dress for Shehzahdi.

"We love her because she's humble and down to earth," Nadirah told The New Paper.

Added Shehzahdi: "She's such an inspiration."

This article was first published in The New Paper.