Pixar can be very difficuly. Maybe, for all we know, Ellie did not even die. Jon Negroni himself said that the rule in movies is that if there is no body, the person is not dead. Maybe Ellie just had to leave Carl. Strange, right? Although I definetly see how Riley is like Ellie. Perhaps Ellie is her grandmother. She probably has memories from them from a photo album. Also, if Riley is related to Ellie, she is also related to Andy, possibly. Maybe they are cousins. It would be especially convenient to move to San Francisco due to the family there. Maybe Carl, Ellie, Riley, and Amdy are all related. I also noted how close in resemblance Bonnie's mom and Riley's mom are. ????