ARIZONA, You are asking some very good questions. And, coming here will help you become better informed. I had a very large tumor in the base of my tongue (too big to safely remove) and was Stage 4.
Chemotherapy tends to sap energy, strength, fluids and the ability to concentrate. Its different with every person, but these symptoms are very common. If she continued to work, even just a couple of hours per week, it might very well help maintain her spirits, give her focus and help keep her motivated. It is surprisingly easy to think about just sitting and doing nothing when the treatments get heavy. There was a period where I couldn't really read. I could see the words, but my short term memory was so impacted that I couldn't remember from one paragraph to the next what I was reading. I also lost feeling in my hands and feet. This made typing and writing pretty challenging (not to mention walking and balancing!!) But those symptoms are short lived. You may need to be pretty patient with her. She may not be completely aware of her limitations.
One of the worst parts of treatment is NOT KNOWING what is really happening. Fear is the mind killer and it makes every symptom much worse. This site could really benefit her. She needs to know what is happening. Cancer is darkness. Knowledge is light. The truth is scary, but not NEARLY so scary as uninformed fear and worry. Grandaughter could benefit too. Don't let that young woman get overwhelmed with this and wind up being your secretary's patient.
What we, here at OCF, have learned about cancer is that fear, hesitancy, reluctance, half measures, being overwhelmed, being too frightened to act - these are the real killers. Cancer can be beaten. Even really bad Stage 4 cancers can be beaten. But only by the active, well informed, assertive and well supported. She is WAY past time for denial. The music has already started and its time to get her a program. You can make a difference for her. We are here to help you, and her, and her grandaughter. Well done to you for being there, but its just starting. Come here often, Tom J