I believe she would have been allowed to tell her "Husband" but no one else. Joe should have never written that little gem. According to Joe, Valerie didn't approve of his book and yet she was engaged and was paid for a Cover Story with her charming snake. Secret Agent?? Me thinks not. Novak got it right. CIA Operative....Dem Operative!!
When Valerie told Joe that she was NOC, they were only dating. On April 3, 1998, Plame became the third wife of former Ambassador Joseph C. Wilson IV. Plame met Wilson, her second husband, at a Washington D.C party in early 1997. She was able to reveal her CIA role to him while they were dating because he held a high-level security clearance. At the time, Wilson was separated from his second wife Jacqueline, a former French diplomat. Wilson and Plame are the parents of five-year-old twins.
It's not illegal for a covert op to blow their own cover -- usually stupid, but not illegal.