My chicken care kit consists of local raw honey (heals all wounds, even horrific wounds like what you've described), epsom salts, oregano oil, turmeric, goldenseal, homeopathic remedies, and protein sources like canned unsalted salmon and cooked eggs.
That's it.
From what I can see, the wound seems pretty serious. It's shocking to me that teeny vicious creatures that look like the cutest Disney characters can squeeze in through the tiniest of openings and wreak havoc on chickens.
If you're able to keep her inside for a good long while, I would create a warm epsom salt bath and flush her neck wounds. You can put her in the kitchen sink and make the solution is a pot so you don't have to actually do a full bath.
You can epsom salts at most grocery stores. If you don't have any local stores, you can flush the wounds with a homemade saline solution. The directions are online. Just boil water for several minutes and then add some salt. Salt in wounds isn't comfy, but I've used it on myself as a saltine solution and never noticed any discomfort.
Make sure you don't hear any body cavity punctures. Chickens have weird air sac things and contraptions I still haven't figured out. You'll hear a soft sucking sound when she breathes if something air related has been punctured. If you do hear something, just use a washcloth as a compress and dip it in the salt solution.
Once you see the wounds, trim the feathers back to fully expose them. There are different approaches to healing her wounds, but one I've found to be exceptionally powerful is raw unpasteurized honey. It's sticky and drips, but honey is water soluble, so you'll be able to wash it off when you feel the need. Coat the wounds with a butter knife and make sure they stay coated and don't dry out.
I'm not sure she can survive this, but as long as you keep her warm and comfortable, give her two or three days for observation. And please keep us posted on any changes.