I actually think this might be an improvement over her previous idea that everyone could only have one friend. If I would say, "Daisy is your friend, and MK, and Bhuvie..." She would stop me and say, "No, Bhuvie is Chlo-Chlo's friend." She would go on to explain, "Delia is my friend," as if no other friends were needed.
More recently on any given day she will announce, "Mommy you are my best friend and AK is Daddy's best friend." Before I can feel too good, she will turn around and say, "AK is my best friend, Daddy is your best friend." And, yes, sometimes the Hoos is LP's best friend too.
I like it best when AK is LP's "best." AK is finally big enough that she can kind of, sort of stand up to LP and I am not completely frightened anytime LP gets into her space. To hear the two of them laughing together is like no other feeling in the world. No one can elicit the quantity or volume of giggles from them that they bring out in each other.
I don't have a sister, but I completely understand what people say about sisters having a special relationship. I am noting this now, beause I am sure in 10 years or so things might not be going so well, but moments like these will be good reminders of what was and what is to come for their long-term relationship.