Welcome to BYC @Dale123 !
Chickens peck each other to communicate,
usually as part of the 'pecking order' to establish and maintain the social hierarchy.
It can be anywhere from mild and not at all a problem,
to an aggressive and bloody mess.
When it gets bad it can caused by many different things, like overcrowding to poor nutrition to a just plain aggressive bird that does not fit into the flock.
Knowing more about your particular situation might garner suggestions to solve it.
This is a behavior that normally cannot be controlled and is referred as "the pecking order". One of the most difficult aspects of chicken raising. Is the case of pecking in your flock somewhat severe? Is any blood being drawn?
Chickens peck eachother to comunicate and establish a pecking order. No way around that.
If you have pleanty of space and Do not over croud the pecking and squabling will be less.
If you have a feather picker you can put pinless peepers on her to stop it.
More info about your chickens and your setup would help.