A lot of good points made here, pro and con. One of the most annoying mistakes in GFIII is the way Vincent dumps Mary. He decides the best time to tell her is as she is entering the opera house, and he more or less says, "oh...by the way, its over between us. Go love someone else." He then puts on his baaaaad hard ass face and poor Mary goes into the box to watch the show. A few scenes later, Mary is enduring the opera, and inexplicably Vincent puts his hand on her shoulder. What the hell kind of mixed message is that?

Knowing that he had to protect Michael from an assassination attempt, and knowing that "everyone" had to get themselves into their car and get out of there and go back to the Villa, the smart thing for Vincent to do would have been to wait until the opera thing was over, the assassin was uncovered, and then break it off. Of course had he done that Mary wouldn't have been whining when she should have been rushing into the car, and she might have avoided getting shot.