"I -- in my opinion, I think he -- it's the onset of dementia," Sterling told ABC News' Barbara Walters on Sunday.
She said that after Donald Sterling heard the tape of him telling his personal assistant V. Stiviano not to take photos with black people or bring them to basketball games, he told her "I don't remember saying that. I don't remember ever saying those things."
"I said, 'Well, this is the tape.' And he says, 'Hmm. I don't remember it,'" Sterling added, as quoted by ABC News. "That's when I thought he had dementia."
Sterling reiterated that she would fight to keep her ownership stake in the team and also told Walters that she plans to divorce her husband.
Separately, Donald Sterling spoke with CNN's Anderson Cooper on Sunday and apologized for his comments while denying that he was a racist.
"I'm a good member who made a mistake," the Clippers owner said. "Am I entitled to one mistake, am I after 35 years? I mean, I love my league, I love my partners. Am I entitled to one mistake? It's a terrible mistake, and I'll never do it again."