I had breast cancer in 1993. Elected the lumpectomy, chemo & radiation as it was in some lymph nodes. Still in remission, but dealing with effects of radiation. They can do so much now.
Ask her what she wants. Everyone has different needs. I needed one person to call per day & they could communicate with others, but I did want that one call a day. Visits, foods I could eat while on chemo, phone calls, cards in the mail, hats. All those helped. I never worried if folks "said the wrong thing". Who knows the right thing every time. Of course, you go through the stages of loss as there is a loss of health for now. Laughter is the best medicine they say. Going to the Lord in prayer was so helpful for me. That's why I say ask what she needs. We are all different in our needs. Peace, comfort & strength for all.