from everything that i've heard, she was cast as and billed so highly as a lead in to a possible Godfather 4 script in which she would have a much, much more important role (rumored to be Vincent's wife).

The other, more confusing question should have been the lack of billing of Sofia. Sure it is obvious that Paramount was trying to take the focus away from her, but truly it is unfair. It should have been in his orer: Al Pacino, Andy Garcia, Talia Shire, Sofia Coppola, and then Diane Keaton.