A little unclear in the article Doc, but it looks like Pelosi's office made the notation in an email to the House Democratic women in the picture.
So, apparently the story came from here - A Snapshot of the Growing Ranks of Women in Congress - NYTimes.com - a NYTimes blog from before the picture was released.
No one tried to pass the photo off as unedited. It was common knowledge, at the time the picture was taken, that the latecomers would be photoshopped in.