A student at Central Saint Martins in London, she began working in Alexander McQueen's studio as part of a work-study programme in 1996.
"We got on very well and he said, "Why don't you just stay?", she told the New York Times.
"I went back to school for a year and I continued working there at the same time. He completely taught me everything."
Quietly assured and meticulous with details, Sarah was Lee Alexander McQueen's first assistant, translating his runway collections into commercial pieces. She was also his very dear friend.
However, tragedy struck in February 2010 when the British designer took his own life.
Due to her close professional and personal connection with Alexander McQueen, the executives at the fashion house decided she was the best-qualified person to assume his role as Creative Director.
Jonathan Akeroyd, president and CEO of Alexander McQueen, released a statement on the decision.
"We are delighted that Sarah has agreed to take on the role of creative director. Having worked alongside Lee McQueen for more than 14 years, she has a deep understanding of his vision, which will allow the company to stay true to its core values."
She has toned down the outrageously theatrical catwalk shows because "that was very much Lee's territory. I can't try and pretend to be Lee."
However, she stated that "creation of modern, beautifully crafted clothes was at the heart of Lee's vision. I intend to stay true to his legacy.”
And the collections Sarah has produced since have earned her much critical acclaim.
McQueen lover Lady Gaga debuted Sarah's first piece since taking over, a custom-made catsuit.
Despite denials from Clarence House and Alexander McQueen, The Sunday Times reported that Sarah won the coveted job of designing Kate Middleton's wedding dress for her royal nuptials to Prince William.
Sarah is said to have caught Kate's eye when she created the off-the-shoulder wedding dress for Tom Parker Bowles' wife Sara Buys in 2005.