Wendy, so sorry about the friend's breast cancer. Well, I got it again, and had the total, and simultaneous reconstruction. It is a lot of surgery with the follow ups. The care was amazing, and I had no pain at all. [Plus eventually a pretty amazing bosom!]
Bluntly, the main thing is whether it has spread either into the lymph nodes, or anywhere else. A scan and tests will show that. If it hasn't spread, then the mastectomy, though radical, stops things in their tracks. I am more than 20 months post the first op . . . at least she isn't also dealing with a MLC spouse!! Man but my xh was mean just before I had the first and major surgery.
I won't say don't worry, but it really can work. And her previous difficulties will give her strength and fortitude.
