• Apollonia
Well, Calo said “She'll make a good American wife”

When Michael was teaching Apollonia to drive [actually it was the other way around! Pacino couldn't drive then!] - Don Tommasino's car drives in, sounding its horn Michael walks over to it and helps Tommasino out of the car as Apollonia runs over and kisses him
Quote
Apollonia: [In Italian] “Michael is teaching me to drive -- watch, I'll show you”
later [pressing the car horn]
Michele - Michele, Let's go -- let's go -- you promised me

My take, for what it is worth!
I acknowledge whilst Apollonia may not have been at the same maturity nor perhaps intelligence level as Michael – not grasping the urgency ie: when Don Tommasino's car drives in sounding its horn nor the seriousness of Don Tommasino and Michael's solemn conversation - Apollonia, at that time was only 16 years old? and been living seemingly a sheltered life in conservative Sicily

Michael was a different man then....loving, protective towards Apollonia She was keen and accepting who he was
Both Michael and Apollonia would have grown together and lived happily for a hundred years!

Godfather 3 - Michael talking to Anthony and Mary about Apollonia
Quote
She was wonderful, beautiful I loved her And then she died
My trusted bodyguard planted a bomb in my car; she drove it before I did