(Nick Galifianakis/The Washington Post)

Dear Ms. Hax: I'm a two-time, currently Stage IV breast cancer survivor. When I was told I needed a double mastectomy, I did the research and decided to "go flat"; I heard too many horror stories about implants and, on the basis of my own personal history, decided they weren't for me.

For dressy occasions, I wear prostheses, but they're not that comfortable. I'm a small, slender (these days: skinny) woman, and barely made it to an A cup even when I was pregnant. It's not that important to me. Most of the time, I don't bother with them.

At Thanksgiving, I worked hard (too hard) to prepare my house and dinner for family; I changed for dinner, but I was tired, and didn't bother putting on my prostheses. My sister-in-law — who vocally disapproved of my decision to go flat — told me, in front of the family, that I looked terrible and was "disrespecting" my company as a result. I thought I was respecting them by knocking myself out on their behalf.

I have to see her and the others again at future holidays. I'm trying to decide if I should make a point by skipping the prostheses, or if I should keep the peace and be uncomfortable.

How can I best handle this? Thanks!

— "Disrespectful"?

"Disrespectful"?: Doing this job puts me in a position to see inside the lives and minds of all kinds of different people in different kinds of pain. That means I get a peek at a lot of bad people and people behaving badly.

Your sister-in-law now ranks among the worst of the worst. I won't soon forget her.

If you can forget her, though, then by all means do. Avoid her completely where possible, and if you must deal with her to avoid losing other people you value, then be sure not to linger — in the conversation, in the room, in the house, in her warped and angry sights.

Should you feel any flickers of guilt, please douse them quickly by reminding yourself that you didn't fight for your survival just to listen to her abuse. Or anyone's.

Maybe there's a decent person under her shockingly awful, boundary-oblivious surface; maybe she harbors a deep terror of illness and mortality, and her way of dealing with it is to vilify anyone she sees as their earthly messengers.

But that's not only as charitable as I'm willing to get — it also, even if true, would be no excuse for her to indulge her mortality fears at your or anyone else's expense.

My flight of fancy is that, if she ever gives you another opportunity, you'll tell her — in front of the family, as she would — where she can shove the prostheses. Even better, calmly ask her to leave your house. Both are ways to handle this to which you are fully entitled.

If such defiance is too much to ask of your nature — and I suspect it is, given your willingness even to consider appeasing Scylla the Sister-in-Law — then please at least rest assured there's no reason or occasion, zero, for you not to rock your finest, flattest, utterly beautiful self.

Write to Carolyn Hax at tellme@washpost.com. Get her column delivered to your inbox each morning at wapo.st/haxpost.