I've always felt that Diane Keaton's acting in that scene was overshadowed by Pacino's. If you watch it closely, you can see her agony so plainly. Because I was so absorbed by Pacino's emotions, I honestly didn't notice Keaton's until recently, but she does an excellent job.
Yeah... I noticed Kay total reaction probably upon watching GF3 the second time... she almost gives way to be concerned about Michael for a few seconds... like mayber she thought she was going to lose him and Mary at the same time... watch her expression(goes from pain to concern)
