The US media personality has been subject to speculation due to her close relationship with long-term friend Gayle King, but confirms if she was romantically involved with her she would be honest about it.
She said: "I`m not even kind of a lesbian. And the reason why the rumour irritates me is because it means that somebody must think I`m lying. That`s number one.
"Number two, why would you want to hide it? That is not the way I run my life."
However, the 56-year-old - who is one of the richest women in the US - does think of the magazine editor as "the best friend everybody deserves".
Welling up, she tells Barbara Walters in a forthcoming ABC interview to be aired later today (09.12.10): "She is the sister everybody would want. She is the friend that everybody deserves. I don`t know a better person.
"It`s making me cry because I`m thinking about how much I probably have never told her that. I`ve never told her that."