Trying to call truce with stepmom for brother’s wedding

Dear Carolyn: My stepmother has been in my life for 20-plus years, since I was a high school junior. She and I have never gotten along well and have had some really terrible fights. I love my dad, but he’s exceedingly conflict-avoidant and says only, “I don’t want to take sides.” So we realized many years ago that we cannot really be around each other much, and I see my dad solo only.
My brother is getting married in a few weeks. My stepmother contacted me to ask whether we could agree not to fight at this wedding. If we pull it off, it will be the first time in years that we have been in the same room without raising our voices.
I have not responded yet because I’m not sure what I’m promising or whether it’s achievable. My dad considers the silent treatment just as hostile as fighting, so not saying anything to each other might backfire.
What are some ways I can be in the same (small, intimate) venue with someone I despise, when pretty much everything she does makes us get into fights?
— Wedding Armistice
Dear Armistice: She “makes us get into fights”? No.
She could be evil incarnate and still, a fight with her involves some degree of choice on your part — to react to her, to engage with her, to raise your voice. You can’t let a remark go unchallenged? Craft a few neutral responses? Force yourself to, if not sympathize, understand Stepmom a little? Bite on a stick? For your brother’s sake?
Getting along isn’t luck, it’s a skill.
Some people require more of our skills than others, and some even prove themselves unworthy of our best efforts. But if there’s someone around whom you must behave yourself occasionally, then there are basic, mature ways to do it — which means that if you can’t do it, then the issue is some combination of your not wanting to and not knowing how.
So here’s my advice. Part 1, for the wedding, pack a whole lot of want-to. You can choose the basics from what I listed above — particularly a few neutral phrases when she says or does things that trigger you, like “Huh, I hadn’t thought of that” or “Interesting.” You can also excuse yourself to get some air or a refill or to say hi to Whatserface over there. And you can hear a trigger from her, breathe deeeeeply, and deflect. “So, Dad, how’s the whatever coming along?”
Part 2, maybe to start pre-wedding but really for the future, please devote focused attention — even counseling — to the difference between reacting based on your emotions and acting based on empathy and boundaries. Understand what is and isn’t your business, and engage/disengage accordingly.

Your laying everything at your stepmother’s feet betrays a basic misunderstanding of such lines. Please trace this enmity, both her contributions and yours, even if yours is merely reacting to her. Then, identify choices you can make differently so this doesn’t own you anymore. Aren’t two decades of rancor enough?