how do I stop the fighting

When you added the three new birds, what process did you go through to do so? How much space, total is available to these six birds?
Now that there are open wounds involved, you will need to isolate her so that she can heal as an open wound is only going to invite picking, even in situation where there is not already aggression going on. Alternatively, you can try using a product such as blu-kote, etc to cover the area and make it not appear like a giant, flashing target for pecking. This will not address the aggression, but will protect the existing wounds from non-aggression based picking.
Integrating new birds is something that needs to be done with an understanding that to the existing flock any newcomers are a threat - an interloper that will take their resources and must, therefor, be driven out/away - or, at the very least, someone who must be put in their place, at the bottom of the pecking order.
Things that can be done to ease the process is to:
1) introduce more than one new bird so there are more "targets" for the natural aggression related to integration
2) house the two groups in such a way that they can see each other, but not make actual contact, for a period of a week or more - this can be accomplished with the use of a dog crate in the existing coop/run or erecting temporary fencing in the coop/run that creates a separate section, or even using a temporary separate pen next to the existing one. This helps get them past the initial "YOU MUST BE GONE" reaction that comes with seeing "strange" birds in their territory and then you have the "this is your place in the pecking order" stuff to go through once they are allowed to mingle.
3) provide LOTS of space for the birds to be in when they start meeting - this allows easier escape if things start getting out of hand. You can also add some natural "cover" items that allow birds to go over/under/etc. to get away from excessive aggression.