Isn't Mandy Grunewald, Hillary's close friend and former employee at the White House, married to Matt Cooper? He probably learned Plame's name from his own wife. It would not surprise me if Valerie and Mandy were also friends, or share a gym, or a preschool, or salon,etc in DC.
You are quite correct. And I wouldn't be surprised at all if Grunwald was the source of the leak. What you said makes perfect sense. Mandy had a new baby (frightening thought) and Plame had 5-year old twins. It would be perfectly reasonable for Plame to have called Grunwald offering advice on nannies, pre-schools, pediatricians, etc. In fact, knowing the Plame/Wilson duo, it seems to me quite likely, given that they were all about moving in the Rat social circles.
My liberal friends are hyperventilating over the brewing scandal and I tell them they are going to be sorely disappointed.