One of the main central themes in this whole trilogy is the influence of your environment on who you become and your action and how difficult it is to escape these influences, no matter how hard you try.

Vito, made the best of it, becoming, as the movie portrays him, a good and noble man, despite his tragic past all of his actions in the movie were in some way noble or for the greater good, overall. Michael on the other hand, is sucked into the family life by the events of GF I, he had little choice, this was a worst case scenario, so he went to the diner and the rest is history.

On the other Connie's evolution I think is a very clear one. In GF I, she is innocent and niave, puts up with the abuse of her husband despite the power she weilds due to her status as Vito's daughter and by the end of the movie comes to a harder realization of things. She realizes by understanding about Carlo that it was for the best.

This is somewhat shortlived and in GF II, for the most part she acts like a teenager, drinking, covorting with men of all types, being reckless and irresponsible. Sounds to me like someone who is trying to rebel or escape her family, huh? She also by the end realizes that she will have little escape from her family and decides to accept it by "remaining close to Michael".

By GF III, many years have passed and she is clearly controlled, confident, clever, caluculating and cunning. Much more Sicilian in her approach, much more like a true mafiosa. She is also in a superficial way at least, much less americanized, and more Sicilian in her mannerisms, stance and dress. She clearly has many of the qualities of her Father and Michael, mature, wise, patient, calculating.

Finally consider this... She is insturmental in getting VIncent to Mike, without that none of GF III wouldn't have happened. She approved of the hit on Zaza, she suggested Vincent take control of the family and Michael accepts. She clearly has enormous influence over not only the family business but over the two protagonists, Michael and Vincent.

Finally, it is my opinion that her feeling toward Fredo and Carlo, are generally accepted as the way things are done in the family, in the Cosa Nostra. This is also symbolic of her transformation, from this innocent girl to a very power and influential figure in the family by application of her natural abilities genetically endower to her by her father.