Plame may be "a private PERSON," but the issue as to whether or not a crime was committed against her is whether or not Plame was "a covert ('secret') agent" or not and/or if she had been within the recent past (as defined by law, think it's five, seven, ten years or something, and any position prior to that defined timeframe is not punishable by law even IF she was of covert status beyond the time protected by law).
The issue is whether or not she even WAS "a secret agent" because so far, everything I've read indicates that she was not.
She was employed by the CIA, yes, but not in any protected, private/covert/"secret" sense at least in the last recent years. Her neighbors knew she worked there. She could be seen coming and going to and from the agency as an employee. It was known to D.C. press that she worked there.
It's hard to figure out what's true and what's not in all the spin, but here's how I look at it. There's only one source that know's Valerie Plame's status without a doubt: the CIA. They're not talking, but their actions speak loud and clear: they reported that a potential violation of the Intelligence Identities Protection Act took place. That tells me this: whatever Valerie Plame's status at the time, it was covered by the IIPA.