Probably raccoon if not an aerial predator.. poor girl..
I've had a duck scalped and a chick.. it's surprising how fast they can heal. How old is older?
What is her usual feed?
She may be in shock.. if you have kennel where she can stay in sight if her flock but still be protected from the rooster you mention possibly mounting her.. If she isn't too freaked out.. make her cozy.. and put feed and water near by.. Do you have any supplements on hand to support her immune system and help her heal?
If she doesn't eat right away, that's okay.. Try to ensure she is drinking something before the evening.. wetting feed if you don't usually.. can make it go down a little easier. A scrambled egg.. is often palatable, easy to digest, and loaded with nutrients.. great for an occasional boost it has 34% protein and 64% fat, with half the protein and a good portion of the vitamins and minerals being in the yolk.
I personally would leave the would alone UNLESS it started to look like it needed help. I let the body do it's thing!
Hope she recovers quickly!