I'm not a chicken expert, but I've had some experience with rehabilitating wildlife, especially silly birds that fly into windows and the like, sometimes head injuries in those silly birds can result in blindness (I've seen this happen to a magpie and a crow in the past five years so while not common it isn't super rare), not saying this is the case with your baby, and she may just be trying to heal...
Ive also seen chickens with nasty head injuries, including cracked skulls make a full recovery after a trip to the vet...I'd personally give her a day or two of TLC and if she's showing no signs of improvement after that, make a decision...if you can get her eating though, that would really help...
Edit: sorry, i derped...the above message is to Dianne...
As for the original poster...
I had a similar thing happen with newborn rabbits the year before last, a rat got into the shed where I was keeping their mother and tried to pull some babies through the cage, had to euth one, and one lost an eye but was otherwise okay...
I'd suggest reinforcing your coop with some smaller grid wire...rodent wire would work, because it is a strong, fine mesh that animals would have a hard time getting to, and if you feel comfortable with it, lay down some rat poison (make sure it is covered to prevent anything friendly getting it)
Either way, I'd monitor the situation closely, I've since put a cheap motion activated camera out where my rabbits are so if something happens I can replay the footage...you could also get some kind of motion activated noisemakers...
https://www.amazon.com/Collections-Etc-Motion-Sensored-Howling/dp/B00TUTA55M
something like that, placed in such a way that the chickens dont set them off, but the nasties do (so facing out from the coop would be your best bet)...I actually use one of those to keep my special needs cat from peeing on the kitchen floor..