The boy who played Anthony (Anthony Gounaris, the little brother of the boy that played young Anthony in Part II) was only three years old during that scene in The Godfather.

This obviously is music to the ears for the ones that firmly believe The Godfather ended in 1950 and it's a decent argument. But, we don't know what she meant with that statement. Maybe she already hated Michael before Carlo was killed, for the fact that the Corleones practically humiliated him by keeping him out of their inner circles and setting him up with a silly job. This led to Carlo reacting his frustration on Connie which severely affected their marriage. And as Michael became his father's heir apparant after he came back from Sicily, she could have also considered Michael to be responsible. And she would have hated Michael even more when it became effident that he had lured Carlo into a trap and giving him and Connie a false sense of recognision and importance. Also, the interpretation of "many years" could differ from person to person.