"As someone who's been in the position of reuniting people ... for her to be the person that's being reunited was certainly a big shock to her," King said. "She wants to get to know her she says, woman to woman, and try to see where it goes, but she is certainly open to having a relationship."
Winfrey's half sister, Patricia, a single mother of two, had been given up for adoption in Milwaukee, by Winfrey's mother, Vernita Lee, in 1963.
"I was 9 years old at the time of [Patricia's adoption], living with my father in Nashville, Tenn.," Winfrey said on her show. "I had no idea my mother was even pregnant."
Patricia, whose last name was not revealed on the show, said she first discovered her link to the media mogul in 2007, after years of searching for her birth mother.
Patricia and her children's decision not to sell the story to the media and to keep the secret for years before meeting Winfrey meant a lot to the media mogul, King said.
"This is extraordinary that somebody would have this information about Oprah, who as you know has been sold out on many occasions by friends, by co-workers, in some cases family, with stories that weren't as legitimate as this," King said. "Patricia wasn't trying to get Oprah, she was trying to find her mother ... having Oprah as a sister, a half sister, was a bonus."
Lee, Winfrey's mother, kept the secret of the adoption for more than 40 years, even denying the truth when Patricia first approached her.
Winfrey told King that the revelation helped her see her mother in a new way. The two have had a tense relationship in the past.
"Vernita, of course, kept this a secret from everybody. Even when Patricia came forward, Vernita was still denying it," King said. "She [Winfrey] said in that moment, talking to Vernita, she realized that she was still holding onto the shame and to say, let it go, release it, we support you, we believe you. What a gift she has given her [mother]."
This morning, Winfrey took to the Internet to see her audience's response to the family news that "shook her to her core," and left her "speechless."
"I talked to Oprah early this morning. She's been up on Facebook, reading all the responses and reading the reaction to the show and what is surprising her is that this has happened to a lot of people," King said.
Family psychiatrists say that not all who are faced with family secrets accept the news right away, if ever.
"It's a dramatic change in a person's life," said Dr. Howard Belkin, a psychiatrist affiliated with William Beaumont Hospital in Royal Oak, Mich. "That shock and disbelief comes in and you can't conceptualize it at first."
According to Belkin, the range of emotions following the announcement depends on the person's stage in life. Often, the older a person gets, the harder it becomes to accept a family secret, he said.
"[Winfrey] may have this regret of more than 40 years of never sharing her successes with [Patricia]," said Belkin.
Although Winfrey was introduced to a blood-related sister, she may also feel more of an acquaintance or, at best, a friendship with Patricia, Belkin said.