DD is good friends with our next door neighbour kid and she comes to play after school most days. I cannot cope with the dynamic though, constant arguing and competing over who gets which bowl, cup, who got the largest food portion etc etc. I've often suggested they don't play together but both children are onlies and they do want to be together and they can play nicely at times.
They are both 6.
How do I adjudicate? It has to be fair because they always play at ours so I can't make DD give way every time.