Speculation is mounting that Miller is protecting herself, that Miller was herself a source of information about Plame that made it to several Bush administration officials and was then recycled to columnist Robert Novak. He, then, disclosed Plame's employment by the CIA and her role in arranging for her husband Joe Wilson's mission to Africa to investigate the Iraq-uranium link.
This would help explain why Miller didn't write a story about the case. It would be difficult for Miller to write a story when she was so deeply involved in how it developed. Disclosure of her role then or now would be extremely embarrassing.
She could be the key to exonerating Bush administration officials of possible violations of the law against knowingly disclosing the identities of covert intelligence agents. If they were simply passing along information from Miller or some other journalist about Joseph Wilson's wife, then they can't be accused of deliberately disclosing classified information about Plame's identity.
The more likely explanation is that Miller is protecting private discussions with administration officials, and that during those discussions she provided or confirmed information about Plame's identity. This would make sense. Both Miller and Plame covered the subject of weapons of mass destruction and it was likely that they knew one another, or at least were aware of each other's work in this field.
Keep in mind that on Mr. Wilson's own website he said his wife worked for the CIA. ANd if Rove didn't get his information from classified docs but from a public source no crime was commited.