Emma is all into relationships - whether someone is her friend, or her "tuzzin",  who is who's mom, dad, big sister, little sister, grandpa, grandma, aunt?... on and on, for nearly everyone she comes in contact with. I am so NOT into who's related to who, but I might be now!
So she gets a little confused when someone is her friend and her sister or cousin. No problem! just combine them, and now she tells me regularly that Leila is her sisterfriend.
I like it :)
They'll be sisters forever --- and I pray they remain sisterfriends for that long too.