In feet, how big is the coop? In feet, how big is the run? A photo showing how they go together might be useful. With only four total chickens your space may be pretty small but if you can put out 3 feeders maybe not. It's easier to give specific suggestions if I know what you have to work with.
When and where do these attacks take place? Is there a specific time or place? What do these attacks look like? Often when an immature chicken invades the personal space of an older chicken they get pecked and run away, if they have room. Typically young chicks quickly learn to not invade that personal space and keep their distance. A single chick or a single older chicken can be harder. Chickens are social animals and want to be with other chickens so sometimes they invade that personal space because they are lonely. Does it look like something like this is happening or is she actively seeking to destroy?
You say the chick is a her, that helps. Cockerels can be even more of a pain when they hit puberty. Typically my pullets do not become a full member of the flock until they mature enough to force their way into the pecking order, usually about the time they start to lay. Until then they avoid the adults, both day and night. But I have a lot of room and I never have just one.
My goal during integration is that no one gets hurt. No more than that. All that one big happy flock can and will come later if you can get to that point. It's puberty you have to get through.
When and where do these attacks take place? Is there a specific time or place? What do these attacks look like? Often when an immature chicken invades the personal space of an older chicken they get pecked and run away, if they have room. Typically young chicks quickly learn to not invade that personal space and keep their distance. A single chick or a single older chicken can be harder. Chickens are social animals and want to be with other chickens so sometimes they invade that personal space because they are lonely. Does it look like something like this is happening or is she actively seeking to destroy?
You say the chick is a her, that helps. Cockerels can be even more of a pain when they hit puberty. Typically my pullets do not become a full member of the flock until they mature enough to force their way into the pecking order, usually about the time they start to lay. Until then they avoid the adults, both day and night. But I have a lot of room and I never have just one.
My goal during integration is that no one gets hurt. No more than that. All that one big happy flock can and will come later if you can get to that point. It's puberty you have to get through.