I too am a cancer patient in remission. I think how your sister would view the flannel with the pink ribbons depends on her attitude. She could view it as a verification that she made it through all the treatments. Or she could view it as an unpleasant reminder of a very rough time. You mentioned that she is very private so it could be it would remind her of the tough time. I have no problem talking about my cancer (lung) and would see the flanel as a big Hurrah that I made it through and am in remission.