The 31-year-old from Gloucestershire - who runs a business producing horses - was part of a team that won the first Olympic team gold in eventing since Munich 1972.
But her success with London 52 comes just eight years after a freak accident while competing at Tweseldown, Hampshire, where she fell off her horse and it landed on top of her.
The accident left her with a punctured lung, lacerated liver, a fractured shoulder and two broken ribs and she was put in an induced coma for several days. She was also left blind in one eye.
Collett, who said she had no recollection of the fall, told the BBC: “Just to be here was more than a dream come true, and to be stood here, with a gold medal, I look back where I was eight years ago – I knew I was lucky to be alive, yet alone do the job I love.”
The 31-year-old has also endured death threats after Kauto Star, a horse who the Cheltenham Gold Cup twice, came into her care following his retirement from racing in 2012.
The horse was sent to Collett to see if he was safe enough to go to someone else to do low-level dressage. But racing fans were furious that Kauto Star was being "demeaned" and that he was not being kept at the yard of his long-term trainer Paul Nicholls.
After the media storm, owner Clive Smith and Collett's coach Yogi Bresner felt it was not appropriate to move him again, Collett explained.
She said the stories were "blown way, way out of proportion" with assumptions that she intended to compete with Kauto Star. Although Collett rode him in a few demonstrations at equestrian events, the retired racing star never competed again.
Collett became the subject of a hate campaign and received the worst of abuse, including death threats, in 2015, when Kauto Star had to be put down due to an injury.
She was accused of lying about the nature of the accident and was criticised for conducting a photoshoot the day after his death was announced.
At the time, Collett hit out at "malicious rumours" that Kauto had run into a wall, and said she had "never cried so much in my life" after he was put down.