Hi Sarah,
If she were my mother, I would first address the pain issue. If vicodin isn't working for her, then her doctors should have tried something else long before now. Call them and DEMAND that they find a protocol of pain management that will manage your mothers pain. If they don't take action, call a different doctor. Once her pain is under control I am quite sure she will feel worlds better and then she can focus on her recovery.
Second I would take care of her nutrition problem. I cwas 41 when I had my radiation treatment, over 30 years younger then your mother, and was in excellent condition when I received my diagnosis of cancer. I couldn't eat enough by mouth to keep my nutrition level adequate for MONTHS after radiation ended. She needs good nutrition in order to heal so I would look into a tube for her. I'm really surprised that her doctors took her tube out so early, and more surprised that they didn't put in a PEG (stomach) tube before she even started radiation treatment. She should be able to handle feeding herself with the tube, either type.
Third, I would address her depression.
It's alot to think about and alot to do, it takes patience to get through it all. But it can be done. You are your mothers advocate right now, a tougher job then being the patient in my opinion. Call the doctors, remind them that they get paid to take care of your mother, and demand that they do their job.
You're in my thoughts.
Minnie