With flawless skin, catlike hazel eyes and straight reddish-blonde hair, the 38-year-old has worked hard to overcome her natural shyness; six years into the role she says her confidence has grown. Sitting in her Milan office, all black leather and art deco lighting, she is dressed in her uniform of black shirt, trousers and high heels - all Gucci, of course. 'I always wear black when working because I use the mirror as I fit the models, and colour on me would distract me,' she says, glancing at the large angled mirror by the door. Her English is heavily accented, and she speaks almost in stream of consciousness without appearing to draw breath.

It has been two days since her spring catwalk show and she is heading down to Florence to make the final preparations for the opening of the Gucci Museum in the city where the luxury leather brand was founded by Guccio Gucci in 1921, and is still based. The fashion show, which marks the house's 90th anniversary with its Jazz Age flapper girls and sharply cut jackets (worn with high-waist, tapering, 1980s-style trousers), was all about decoration - with a judicious amount of Gucci's signature flash. Jackets featured graphic art deco (or 'hard deco', as Giannini calls it) patterns worked in black, white, gold and touches of green, while the beaded flapper dresses were inspired by New York's famous art deco Chrysler Building.

Giannini's father was an architect: 'I always say it is my second passion after fashion. I grew up with a strong visual appreciation of architecture; it is something I like along with interior design.' Her home in Rome has an art deco interior, she says, adding that her team joked: 'This collection is perfect in your house.'

Her interest in architecture and interior design led to her close involvement with the creation of the Gucci Museum, which opened at the end of Milan Fashion Week, when the fashion crowd decamped to Florence for the event. 'When I joined Gucci in 2002 and first visited the archive, I fell in love with all these incredible objects, like the handbags, which span the 1920s to 90s. You see the history of Italy, the culture and the quality of craftsmanship in Florence. Everything was made there and at least one person in every family worked for Gucci.'

Until Giannini moved her design studio to Rome to be nearer her parents, she used to work in the beautiful 15th-century building that is the new museum in the Piazza della Signoria (next to the famous Palazzo Vecchia where the glamorous launch party was held). Originally, the archive was in Milan 'and was very difficult for me and my team to visit. Then when I moved the design studio to Rome, I wanted to keep the building in Florence and the idea came for the museum. The building is so beautiful that it would be a shame to not share it with the people,' she says.

Giannini's love of the archive and researching Gucci's colourful history is a result of the years she spent with her art-history professor mother, visiting galleries such as the Louvre Museum and Tate Modern. In the archives, she found the gold-plated tiger's head that came from Gucci's 1970s heyday and is a motif for the new summer collection. This, she explains, 'then reminded me of the 1920s high jewellery collections of Cartier and the art deco era'.

Gucci is not a conceptual brand: at times Giannini's vision is ruthlessly commercial. However, she has won over fans by replacing Ford's turbo-charged spike-heeled vixens of the 1990s with a new softness and femininity, and tapping cleverly into the brand's DNA. She has updated must-have accessories such as the Flora and the totemic bamboo-handled bags.

Aside from the 1979 Gucci customised Cadillac, discovered in Florida (as part of the 90th anniversary, Giannini has customised the Fiat 500 and the Riva speedboat), the museum features more familiar products such as the luggage, the red carpet dresses and a special display of the Flora handbags, vintage scarves and chinaware - it is as much a classic to Gucci as the horse-bit and the bamboo.

The Flora bag was one of her great design successes after she was made creative director a year following Ford's departure. She worked her magic on a collection of bags and shoes inspired by a pretty Flora print scarf designed in Rome in 1966 as a gift - an elegant flowery alternative to a bouquet - for Grace Kelly (Princess Grace of Monaco) when she visited the store.

'I remember this scarf from when I was a child because many women in Italy in the 1970s and 80s wore the Flora scarves - my mother had one and my grandmother - and when I joined Gucci I saw all these incredible things in the archive and thought it would be interesting to do something with accessories.'

Giannini's fashion gene was probably donated by her inspiring grandmother, Luciana. She owned a dress shop in Rome and, as a child, Frida would spend her afternoons there after school.

Despite her parents' doubts (her father would have preferred she studied architecture) she studied fashion at Rome's Academy of Costume and Fashion. In 1997 she joined Fendi, first working in ready-to-wear before moving to leather goods. It was the height of the Fendi baguette mania and although she denies inventing the coveted shape, she was responsible for turning out hundreds of variations. She came to the notice of Ford, who hired her in 2002 to design handbags for Gucci in his London-based fashion studio.

When Ford left Gucci in 2004, Giannini became part of a triumvirate of creative directors who led the brand for a year: Facchinetti designing womenswear, John Ray menswear and Giannini on accessories. Asked, in light of LVMH's search for a replacement for John Galliano, whether big fashion houses need a 'name' designer at their head, she is emphatic in her reply.

'Yes, especially for a brand like Gucci. We tried in the past with a team of people and it didn't work at all because I think lovers of Gucci really want to see a person who embodies the soul of the brand. As a designer you put a lot of your personality into whatever you are doing. There is a reflection of yourself in the products and,' she adds with a laugh, 'they need my face to sell it.'

Giannini is a perfectionist; she's quietly determined and copes with the pressure her role brings by being organised and having a good team of people around her.

It is horseriding, her love of cooking and her German shepherd dog that keep her grounded, she adds. She has a house not far from Rome where she spends her weekends and her horse in stables nearby. She began riding when she was six and became an accomplished showjumper. Giannini recently separated from her husband and there are rumours that she and Gucci's recently appointed chief executive, Patrizio di Marco, are more than just colleagues.

Another method of depressurising after a day in the studio is music. 'I have a collection of about 8,000 vinyl records.' Her taste ranges from classical to opera to 1970s and 80s pop. She is now listening to French chanteuse Edith Piaf, but at the Gucci Museum launch party she was shimmying in her Gucci art deco flapper dress to the songs of Debbie Harry, whom she describes as her icon. After a memorable and pressure-packed year, it was the perfect way to see Giannini let off steam.

Signature styles

GG logo Guccio Gucci's initials first appeared on the clasps of his handbags in the 1960s, then as a monogram pattern on luggage. It made a ghetto-fabulous return in the 1990s and has been rendered modern and chic by Frida Giannini in her latest bags and iPad cases.

Bamboo The bamboo-handled bag (above) was introduced in the late 1940s as an alternative to leather, and now is the latest word in luxury. Tom Ford revived it for brightly coloured bags in the 1990s and it now features in bags, belt buckles and jewellery.

Horsebit The horsebit motif (below) is used to distinguish Gucci's shoes from mere loafers. It features as a fastening on luxury handbags or silver and gold bracelets, along with the GG and other iconic insignia.

Green and red webbing The striped 'girthstrap' canvas is a byword for luxury. It has been recoloured a few times and appeared on bags and belts, but the spirit remains the same. Gucci maintains its horsey connections, sponsoring show jumpers like Charlotte Casiraghi.

Flora It began as a dainty flower print scarf for a princess and must have been worn by every Italian woman in the 1970s. The pattern has appeared on dresses, handbags and chinaware; it gave rise to the name of one of the house's perfumes.

Collaborations In the past year, Giannini has given the Fiat 500 and Riva speedboat a Gucci makeover, but she wasn't the first. A Cadillac, recently rediscovered in Florida was Guccified in 1979 with GG upholstery and go-faster stripes.