Speaking to Grazia magazine, Slavica, a former model from Croatia, said: "I don't care how much the wedding cost, as it was once in a lifetime occasion."
"It was worth every penny because it made my daughter happy. Who cares about money?"
CLICK ON PHOTO FOR FULL GALLERY
Slavica, 53, added that she wanted to make the day special as her own wedding to Bernie was a disappointment.
Their 1985 ceremony was a no-frills affair at Kensington and Chelsea Register Office in London, with only the groom's F1 associate Max Mosley for a witness.
No photographer was present to capture the moment. And when the newlyweds found out that the restaurant of their choice was booked up Bernie went back to the office, leaving his new wife to make her own way home.
With the end of their turbulent marriage in 2009, the statuesque brunette received a £750-million settlement meaning she could afford to splash out.
When her 22-year-old daughter married businessman James Stunt in August, 6ft 2in Slavica made sure that the lavish wedding was "everything it could be".
The fairytale nuptials, set at a medieval castle just outside Rome and costing £310,000 to hire, featured the bride in custom-made Vera Wang.
Guests toasted the happy couple with £4,000 bottles of Chateau Petrus wine and watched performances by the Black Eyed Peas, opera star Andrea Bocelli and the Royal Philharmonic Orchestra.
Bernie recently revealed his shock at the staggering cost of the wedding, having originally been led to believe that the day had cost in the region of £5 million.
"My younger daughter got married and I thought as father of the bride I should pay for the wedding" said the 81-year-old mogul.
"But when it was suggested how much they would be spending on drinks, I thought it was absurd and I managed to upset my daughter and my wife."
"Then she spent in excess of £12 million on my daughter’s wedding which I did not know about until afterwards."