Your chick's wound is identical to the one a chick of mine had several years ago after the rooster scalped her. I wrote the entire thing up and posted it in the comments section under my photo album on my personal page.
https://www.backyardchickens.com/g/a/5992343/default/ Scroll down and you'll see it below the photos.
It chronicles the treatment and healing progress my chick went through, and the mistakes I made along the way so you don't have to make them. It's worth reading if you aren't sure how to care for a serious wound like this.
Your chick has a much too large a wound for Blu-kote, and it will dry out the wound when it's imperative you keep it moist. It will not heal and infection is much more likely to set in if the wound is allowed to dry out.
Infection is your biggest danger, therefore, it's very important to clean the wound twice a day, morning and before she goes to sleep. I describe how I did it.
Keep the wound moist with any anti-bacterial ointment.You can use Vetericyn along with the ointment, spraying the Vetericyn on the wound first, following with the ointment. I happened to have some Silvadene, a burn ointment, on hand so I used that. It tasted bad so the other chicks left her alone once they had sampled what she was wearing on her head. It was a blessing she didn't need to be segregated. You might be able to return your chick with the others and see what happens after it begins to heal.
Your chick's wound is going to heal from the outer edges inward toward the center. It took about six weeks for my chicks to grow new skin and there was a tiny pinhole left finally. I faithfully continued to treat her wound until the morning I finally saw that the pinhole had closed.
At one point, I got lazy about caring for the wound, and I noticed that the healing progress had stopped. The wound had been allowed to dry out, and new skin wasn't able to be formed because of my neglect. I urge you to take this very seriously, or you could lose your chick. It's a very serious wound, and I doubt the chicks did this to her. Either a larger animal got a hold of her or she got herself stuck in something and lost her scalp. You need to investigate how this happened and not simply assume the other chicks did it, which I think is unlikely.