Hens can attack and peck necks as well, but the suspicion would be more for the cockerel. Some are overzealous at girst, and may calm down if they are separated for awhile. But I have removed one permanently who did that to my half blind polish hen once.
The pine shavings can get into the...
Your pullets injuries are moree serious than some. Watch for a bad odor or other signs of infection. There a number of threads on BYC about similar injuries, and here is one to read:
https://www.backyardchickens.com/threads/scalped-chicken-still-alive.1091319/...
Poor girl. Separate her in a dog crate or pen with food and water. What do you have for cleaning a wound? Chlorhexidene 2% is very good, but you could also use Betadine, saline, or mild soap and water. Vetericyn or a similar hydrogel wound spray from the feed store would also be fine. Then after...