I'm glad she is doing well, that first photo looked bad. As for rats, it could be. And is even likely. But I would never use poison baits. A few reasons. One, I have seen rats die from poison bait, and it is painful. Even though you want the rats gone and they are a pest, I believe in doing it as humanely as possible. More importantly, if one of your birds (or an other animal like a cat or dog) eats a rat that has ingested the poison bait it will kill them too. I suggest getting snap traps, they make types that the chickens can not get to. The rat would have to walk into box, in the box is the trap. Line the traps against the walls. Rats will always follow the walls and other solid objects, they do not willingly cross open ground.