Adding chickens to chickens

Yep, seperate her.
You can do a couple things. Remove her entirely (keep her in the house, or where ever) for a couple days, or make a pen inside their pen where she can stay and see the new ones but can't hurt them.
Removing her will take her out of the pecking order and she will be the "newbie" once you put her back in. Making a pen inside the pen will pretty much force her to get used to the new ones.
When you reintroduce her, supervise them and make sure nobody gets hurt. Hopefully this process won't take long, but sometimes it can take a few weeks of just letting them hang out together for short periods of time.

 

I don’t house chickens of different ages in the same coop in the beginning. I have two coops next to each other so they can see each other, when I let them out to free-range they will usually stay together in their group until they are around the same size and have had a chance to work on their pecking order. They will usually work things out if not we will help them get along by culling out the aggressive chickens.

 

when we did our coop we fixed a area just for peeps and it works great they see them all the time so don't get upset when we let the peeps out of cage which is when they can eat anything. about 7 to 8 wks old
the picture showing peeps cage they look at each other all the time this way