I think Ellie has an imaginary friend. Her name is Lily. She has been around for a few months now and, although Ellie doesn't call her an imaginary friend, I am not quite sure what else you would call her. At first I thought that Lily was one of the many names Ellie gives her various stuffed animals, but now it seems clear that Lily is her own, invisible entity.
Here is what we know about her so far: Lily lives in California . . . specifically in Ellie's house in California (Ellie has never been to California but regularly tells people she lives there). Sometimes Ellie says Lily is her friend. Other times she says that she is Lily's mom "and takes REALLY good care of her." We don't know much about what she looks like, only that Lily has "two pony tails, not just one." And her hair is all different colors, "like red in the front and purple in the back." She loves ice cream. She has a strict policy of only wearing dresses.
Lily often comes up when Ellie is trying to deflect attention from some sort of mischief she has gotten into. For example, if I say, "Ellie, don't push Brendan. That isn't nice." Ellie might respond, "But Mom, Lily pushed her brother (oh by the way, Lily has a brother named Frank) and her mom told her that it was fine to push brothers and knock them down." Other times Brendan is prohibited from sitting next to Ellie on the couch because "Lily is sitting there and Brendan is going to totally smoosh her."
Certainly more to come on this interesting development.