I think some (or someone) in Val's group outed her themselves just to be rid of the Wilsons.
The Kristof and Pincus articles and Wilson's op-ed were embarrassing for them because it showed how casual they were about sending an ex ambassador to do a spook's job and they hadn't even bothered to put him on a leash.
Wilson's mouth was a liability for them and they suspected Val was telling him more than she should about Company business.
Val wasn't going on junkets anymore because of a previous outing. She was doing good work, but she wasn't able to do much of what she was trained for. Damage would be minimal, so screw them.
They were the ones who slipped 'Valery Plame' into the gossip stream to punish the Wilsons.
Beyond that they didn't much care how it played out or who would be blamed.
Unless Fitzgerald is hiding it on purpose, there is little in the public record regarding who knew the actual name 'Valery Plame' (Miller's notebook and Novak's article) and nothing showing anyone in the administration knew or related that specific datum to anyone else in the administration. How did the fact of Mrs. Wilson's CIA employment get from Mrs. Wilson/Wilson's wife to Valery Plame?
I doubt we'll ever know.