I've got a 20wo Orpington that does the same thing. She's a Lavender Orpington and as pretty as a picture when her beak is shut. When she opens it the most grating and raucous sound comes out. Her Orpington hatchmate doesn't make much noise at all but I've never heard Ophelia sound like a goose like my pretty Violet does.
Age is a very important piece of information no matter the subject.
In this case, the honking isn't necessarily from her voice maturing, (most chickens' voices start changing at 16 weeks) although it's probably related in a small way. I'm only guessing here, but her pale comb and delayed development could have something to do with being injured by the predator. There are some very fragile but important organs lying just below the surface of her back. If the predator injured her in that region, her reproductive system and lungs could have been damaged. If her ovary isn't functioning, it could mean she will never mature. She may never lay eggs, or if she did before, she may no longer be able to.
Another cause for her strange honking might be from a tumor in her trachea where her voice comes from. And the third reason for strange sounding voice noises can be from respiratory disease, either bacterial, fungal or viral.
Don't let any of that scare you. As long as your hen is merely honking and is otherwise normal and healthy, try not to worry. And she may be completely normal and is just maturing slowly.
Sometimes vitamin E oil 400iu and B-complex can help repair neurological damage. It will hurt nothing to try it. Get the people vitamin E oil capsules and B-complex tablets. Give her one of each each day. A sliver of a selenium tablet about 25mcg worth will help the E get absorbed better. Or you can feed her an egg every so often since eggs have selenium.
It probably won't improve her honking voice, though. You could always name her "Mother Goose".