My guess is that Miers was very publicly invited onto Marine One and taken to Camp David as a face-saving gesture. I don't imagine she played any real role in the selection of her successor.
Of course I can't prove it, but surely her objectivity at this point would be questionable.
Well, she is White House Counsel so I imagine she reviews every judicial nominee. The President is a kind and compassionate man but, I doubt, he appoints the White House Counsel on this basis.