Isn't she White House counsel, not Presidential counsel? I hate to try to pull a civics lesson out of The West Wing, but I remember the White House counsel on the show covering everyone, not just POTUS.
Regardless whether Meirs is subpoenaed, they're going to go after Rove. In a way, this mirrors Clinton somewhat -- keep trying and trying and trying and finally get him for something. Except that in Bill's case it was a blowjob and in this case it's a gross misuse of political power.