I don't get it

So for the most part, both girls get a long fairly well.  Audrey is getting better with keeping her hands to herself and for the most part is actually getting to be an easier child.  But sometimes we have scenes like this.

Okay so Audrey is wearing Celia's boots and her sweatshirt jacket and is carrying her doll blanket.  There is no objection to this, she is fine with her sister borrowing these items.  What is the argument over???  Ice packs.  Yep, they are arguing over who gets to carry around which ice pack.  This is not a one time argument either.  I have stopped intervening in it and they do eventually work it out but I still am puzzled as to the appeal of an ice pack.  They do not even argue over our elmo or piggy boo boo ice packs, nope it is the boring old ice packs we put in coolers.