I would be surprised if she wasn't still sore given all the tissue that was removed. Remember that the radiation is also going to slow down the healing process as well. My neck was sore for a good 6 months after surgery, that is the part that wasn't left permanently numb as a nerve bundle had to be cut during the removal of my nodes. The accumulated lymph fluids which now have no where to go (and which will take some time to find new pathways) also make this area feel unusual, though I wouldn't define it as pain. If you are thinking that they missed some cancerous material, just remember that cancerous nodes are usually painless, and this is probably residual discomfort from the surgical procedure.