John Edwards' daughter speaks on father's affair

Updated 10:44 PM ET

NEW YORK The eldest daughter of former Democratic presidential candidate John Edwards says it was difficult to watch the experience her parents went through after he revealed that he'd had an extramarital affair.

Cate Edwards spoke in an interview scheduled to be aired on NBC's Today show Friday morning and on "Rock Center with Brian Williams" that evening. She said her father told her of the affair and that she was devastated by the news, adding that it was hard to see them go through the ordeal. The 31-year-old attorney's comments were reported Wednesday on the Today website.

"I guess he and my mom decided that that was, you know, how it needed to be done. So yeah, I was devastated. And I was disappointed," she said. "I mean, these are my parents. I had grown up with a lot of love in my family. And it was hard to see them go through this."

Elizabeth Edwards died on Dec. 7, 2010 after battling cancer.

"I miss her in sort of big ways and small ways," Cate Edwards said. "You know, it's big things that go by, like my wedding. She wasn't able to be there. But we got to talk about it. And I felt incredibly lucky that I got the chance to even have that conversation with her.

"And I sort of carried out some of her vision which was great to sort of feel her presence there even though she wasn't actually there. And then there are small things. I mean, I get away with bad grammar. I never used to get away with bad grammar."

John Edwards' campaign finance fraud case ended in a mistrial last May when jurors acquitted him on one of six charges but were unable to decide whether he misused money from two wealthy donors to hide his pregnant mistress, Rielle Hunter, while he ran for president.

Cate Edwards was by her father's side during the federal trial in North Carolina.

John Edwards also has a teenage daughter, Emma Claire, and his youngest son, Jack. His son, Wade, died in a car accident in 1996.

He said after his trial that he planned to spend more time with a daughter whom he fathered with Hunter, Francis Quinn Hunter.