@Lynjoan every breast cancer is different. In my case I have triple negative. My surgeon did not recommend a double mastectomy even though I also have the bracken2 gene. The reason was this type of cancer if it returns hits brain /bone.ovaries not breast. Radiation oncologist confirmed this opinion.
So getting my breasts removed is pointless. I had another friend different cancer wanted breasts removed as didnt want the worry of mammograms.
So having a secondary breast removed is no guarantee cancer will not return. Of course trust your instict . My personal belief is if there is nothing wrong with any part of the body leave it alone.