"I haven't faced the devil in the face because I was in the gutter at that moment," she tells Oprah Winfrey. "So I'm aware of the fact that I've been drinking, you know, that I was not in my right place."
The 50-year-old Duchess of York has previously said she was "devastated" by the scandal. On the tape, she tells an undercover reporter, "I can open any door you want" to Andrew, a British trade representative.
The interview on The Oprah Winfrey Show airs Tuesday.
Ferguson, who spoke to Winfrey in Los Angeles on Friday, returned home to the U.K. over the weekend to her supportive children: Princesses Beatrice, 21, and Eugenie, 20.
Additional reporting by SIMON PERRY