Spencer told Good Morning Britain, "I hope she'd be pleased the truth is out to the context. She was taken into a very dark place, her paranoia was fed."
And former BBC director general Lord Tony Hall told a parliamentary committee on Tuesday that he was "sorry for the hurt caused" to the family by the scandal surrounding the interview. Bashir will not face criminal charges.
Lord Hall said of the decision to keep employing Bashir despite his questionable tactics, "I trusted a journalist. I gave him a second chance. We, the team, gave him a second chance, and that trust was abused and was misplaced."
Prince William has strongly criticised the way the interview was obtained, saying, "It brings indescribable sadness to know that the BBC's failures contributed significantly to her fear, paranoia and isolation that I remember from those final years with her."
On July 1, which would have been Diana's 60th birthday, a new statue to her will be unveiled by Prince William and Prince Harry as the world remembers the princess, who died in a Paris car crash nearly 24 years ago.
Spencer said it will be an "emotional day".
"I remember my father always used to talk about the day Diana was born, 1st July 1961, and it was a sweltering hot day and this wonderful daughter appeared. It's so funny to be of an age now where your slightly older sister's 60. It will be an emotional day, but it will be a tribute to a much-missed and much-loved sister, mother, etc."