nest box fighting

One of my RIR's has FINALLY become broody - she's been sitting on the nest for about a week now. I was ecstatic when I realized what was happening, because they have been great egg layers, but this is the first time any of my hens have been broody!! The problem is, her sisters keep trying to run...

We finally found Mabel a flock made in an older girl name Ruby this was their first nest box fight

I have nine laying hens and three nest boxes. This morning, one of my hens kept chasing two other hens out of whatever nest box they tried to lay in. One of the hens got injured (she is bloody right behind her comb). I rescued the other one as soon as she laid. Two questions: (1) How do I...