I am a BC survivor. The only place I talk about it is in my BC support group. I go there to support the newbies, because it was such a great help to me when I was just out of chemo. If your sister doesn't want to talk about it, she probably doesn't want reminders of it. Unless you feel comfortable enough to ask her about the backing, don't use it. If one were given to me, I would say thank you and never use it.