The doctor said it was cancer? She was tested for it and that is the official diagnosis? Or was this just a guess or suggestion?
If I were told I had cancer, I would worry too. But I would also consider the source, and consult another. It is hard to go forth with a trusting heart, and assume the best, but that is the first step to beating whatever it is. Worry and defeatism will hamstring the immune system.
Lead her toward enlightenment and learning, and plot a strategy for the annihilation of the source of her illness, whatever it is. Taking positive steps changes the focus from fear and sorrow to the warrior's path to victory. I am praying that the two of you will raise your fists together, and vanquish the as yet unnamed foe that has attacked. The Lord that created you will rejoice in your triumph. Be strong for each other, and bless you.
Killdeer