#137 should explain where she got her info.
No doubt whe would have talked to Ritter, and numerous others. There were plenty of her associates mentioned by name in articles, like Cooper's, mentioning Thielman, Wilson, Foley, etc. Ritter was out of government the loop since 1998, and dicey because of his Iraqi contacts. Unless you can show me otherwise, I think Miller had plenty of other ways to find out about Plame than Ritter. Could have been Plame herself.
The lefties miss who had the biggest motive to revenge against Wilson. Namely, George Tenet. Did he, I don't know. But if Tenet, Miller might be scared to talk.