CHARLESTON, S.C. - South Carolina first lady Jenny Sanford writes in her new book that she got short of breath and later felt unwanted and ugly when she found out about her husband's affair with an Argentine woman.

Sanford also writes that one of her sons exclaimed that it's "worse than Eliot Spitzer" when she told them about Gov. Mark Sanford's infidelity.

Spitzer is the former New York governor who resigned after acknowledging he was a client of a call-girl ring.

Jenny Sanford's memoir "Staying True," published by Ballantine Books, an imprint of Random House Inc., goes on sale Friday.

She will be interviewed by Barbara Walters on ABC's 20/20 on Thursday night. A segment of the interview aired last month, a few days before she filed for divorce from her husband of more than 20 years.

The divorce will be final later this month.

Mark Sanford disappeared from the state for five days last summer, and his staff told reporters he was hiking on the Appalachian Trail.

But he was really in Argentina seeing his mistress, Maria Belen Chapur, during a trip that was supposed to be an economic development mission.

Mark Sanford, who later called the other woman his "soul mate," publicly confessed the affair during a Statehouse news conference upon his return.

Jenny Sanford said she discovered the affair in January 2009 when she found a copy of a letter her husband wrote to Chapur. She said in the ensuing months he asked several times for permission to visit his mistress.

Jenny Sanford, a Georgetown-educated former Wall Street vice president, moved out of the Governor's Mansion last summer and is living with the couple's four sons at their beach house on Sullivans Island.

Mark Sanford's office declined to comment Monday.