I would add that egg yolks are healthy for chickens, and would be easy for her to eat. This sounds to me like either a bad case of Bumblefoot or a broken/sprained bone.
If you post pictures of your hen's leg/foot, I can tell you if it's Bumblefoot.
I had a hen with a very severe case, and her symptoms were: swollen leg, red coloring to leg, fever, lack of appetite, limping.
Bumblefoot is an infection of the inner foot caused by a heavy impact. When the chicken recieves a heavy impact to their foot, the tissue can get injured. When this happens, pus builds up around the tissue. Birds have a different type of pus than humans; it is hard and build up into "kernels." In mild cases, before the pus has a chance to harden, you can treat Bumblefoot with antibiotics. I use an injection of a half cc of Tylan 50 for cattle for standard size birds (you can but this at most farm supply stores). In severe cases, the pus Bumbles must be surgically removed. You can do this at home, and should you want it, I can give you an illustrated tutorial.
For now, keep her away from the flock in the garage/house. Always provide water and Eggcessive above had some excellent suggestions for food options.