After Dinner Squabbles

Difficult to explain this question proberly so please bear with me ,we've always known that gemma (lab )has a thing about her food bowl (bit grumpy about its being taken from her even when empty)so we feed ruby in another room to save any trouble .thats not the problem ,once they have both finished and both bowls are lifted we've noticed that ruby will sometimes stare at gemma very intently ,untill at last gemma will bark and chase her away ,thats usually the end of it,and nobody ever gets hurt ,just occasionally its reversed except that ruby never chases gemma ,is it just a game or is it what my freind suggested that ruby is trying to "take gemmas crown"any suggestions welcome .