You know, I've had some chickens with respiratory problems this winter that would get some dark red patches (due to lack of oxygen). Any sneezing at all with her? The first picture looks similar the second looks like a bruise. I had a rooster that had scaly leg mite that caused an infection in both knees. I eventually had to put him down because of it but his infection was much much worse here.
I'm looking at the legs and I'm thinking 1) infection or 2) oxygen levels. I'm looking at comb and thinking internal external parasites. Some of those darn parasites though will invade the lungs (both internal AND external parasites) and that can cause problems with oxygen levels. Respiratory problems are not always obvious.