All I really did was spend alot of time out in the pen with my girls, trying to referee some! They still peck each other, but it is not as bad as it was. I am by no means an expert on chickens, we just started our flock in April, but from what I have read if your little leghorn is being pecked too badly, and she has a sore spot that has bled, then you may need to seperate her from the other chickens, because they will peck her sore spot and make her bleed more and I think they can actually kill her. But, like I said I am not an expert on chickens. My husband said to try seperating the leghorn from the others by doing a two foot by four foot area for her for a little while until she heals up.
Use chicken wire so the other chickens can see her and she can see them, she won't like being confined in such a small area, but at least she will heal and maybe the other chickens will get used to her. You just have to spend as much time with them as you can while they are acting bad, that is what I did. I hope your girls start getting along soon, it is very stressful when they are acting like that.
Sorry I couldn't give you any better advice.