Hen Bullying!?!?

[SirMelon07]

so recently one of our smallest hens in our flock of nine hens begain to hide in the roost and poof up when we opened up the pen to collect eggs that the others left. We soon had to force her out because we never saw her leave her spot and we began to worry she would starve herself. She ate some oats we give to our hens as treats (for training and spicing up their diets ･◡･) and after we led her to where the other hens were eating grass.
When she was introduced to the other chickens, she immediately poofed up and croaking in a more threatening manor. And when the other hens saw her, a couple came and tried to attack her (or try to run her off, as we had also seen the same hens scaring off our dogs). We think the flock just doesn't like this one hen, or had lost her scent (or something like that) and just think she is a stranger coming to take their food.
Please help ˚‧º•(˚ ˃̣̣̥᷄⌓˂̣̣̥᷅ )‧º•˚

 

[Celeste Cannon]

The hen that puffs up and doesn't move from the coop is probably broody. That means she wants to be a momma. She is trying to hatch some eggs, but she can't unless you have a rooster. She is a bit aggressive to the other chickens because she wants to protect her eggs. You should move her away from the other chickens if you want her to continue being broody, but if you want her to stop just keep destroying her nest until she gives up trying to hatch her eggs. This is a good chance to hatch some eggs and get baby chicks however. You can buy some fertile ones and put them under her to hatch and raise herself. Good luck! Let me know if you need any more help!