In her first extended comments on the affair, Sanford recalled how her husband repeatedly sought permission to visit his lover in the months after she discovered his infidelity.
"I said absolutely not. It's one thing to forgive adultery; it's another thing to condone it," she told The Associated Press during a 20-minute interview at the coastal home where she sought refuge with their four sons.
The Sanfords had separated about two weeks ago. She said her husband told the family he wanted some time away to work on writing a book and clear his head. The first lady said, "I had every hope he was not going to see her."
"You would think that a father who didn't have contact with his children, if he wanted those children, he would toe the line a little bit," she said.
Mark Sanford, who is staying at the official residence in Columbia, returned Wednesday to end days of speculation on his whereabouts, publicly confess his cheating and emotionally apologize.
Jenny Sanford, a Georgetown-educated, former Wall Street vice president, did not stand next to her husband Wednesday during his pained public confession.
Sanford said she discovered her husband's affair early this year after coming across a copy of a letter to the mistress in one of his files in the official governor's mansion. He had asked her to find some financial information, she said, not an unusual request considering her heavy involvement in his career.
She would not comment on what was in the letter except to say "enough to figure out an affair was going on."
She felt "shocked and obviously deeply hurt. I didn't think he had it in him," she said. "It's hard to find out your husband is not who you thought he was."
The first lady said she confronted her husband immediately, and he agreed to end the affair. She said she wasn't sure Friday whether he had done so.
"I guess that's what we will have to see. I believe he has," she said. "But he was down there for five days. I saw him yesterday and he is not staying here. We'll just see what kind of spirit of reconciliation he has himself."
The governor declined to discuss details of the letter and how he handled it with his wife.
"This goes into the personal zone," Gov. Sanford said Friday. "I'd simply say that Jenny has been absolutely magnanimous and gracious as a wonderful Christian woman in this process."
Jenny Sanford cried at the end of the interview, and said the couple have been to counseling.
"When I found out in January, we both indicated a willingness to continue working on the marriage, but there's not room for three people in a marriage," she said. "I've done everything in my power possibly to keep him from going to see her and to really make sure she was off the table, including asking him to leave."