Exactly, it just doesn't make sense.
She must be protecting a Dem source.
I am liking more and more the theory that Plame is Miller's "source".
Everything fits.
1. They both had an interest in weapons of mass destruction (Miller wrote about them, Plame "worked on WMD" for the CIA) and it is very possible that their paths crossed. Maybe they crossed because Miller is a relentless, veteran reporter, or maybe they crossed somewhere along the Washington DC cocktail circuit.
2. It explains why Miller doesn't trust her source's waiver of confidentiality - - as an employee of the CIA, Plame could indeed have been "coerced", and it is likely that Miller figured this out. (By the way, I have no doubt that Fitzgerald KNOWS who Miller's source is - - he just needs her to testify to it.) In the same vein, it explains why the "source" has not stepped forward even after waiving confidentiality - - Plame's fellow travelers at the CIA, likely including those immediate superiors who signed off on the Wilson-to-Niger scheme - - have somehow let the NY Times know that they do not want Miller to name Plame.
3. If Miller tesifies that her source was Plame herself then that would completely exonerate Rove, and that is something that the New York Times and their Democrat Party cannot allow.
Everything fits.