You tried everything to get your fiancé's mother and your own mom to like each other before the wedding, but nothing worked. Your fiancé tried to help, too, but made absolutely no progress. Every occasion you're all together feels like torture as you desperately try to find a topic of conversation that everyone finds interesting. And it's making you dread your own wedding.
Maybe one mom is the troublemaker, and the other the victim. Or perhaps they're both behaving badly. No matter. It's up to you to do everything possible to make both of them comfortable so that you can enjoy a drama-free wedding weekend. If your mom is the one responsible for the bulk of the problem, you can try sitting down with her for one last-ditch attempt to make your entire wedding experience more pleasurable for everybody. But don't put her on the defensive or you could make things ever worse.
The best case scenario, in a situation like this, is that both mothers tolerate each other well, even if they're never going to be besties. Polite disdain is far better than open insults. A "Cold War" is preferable to mad drama. If you know that's how things are, you have to be prepared for it.
You've tried to improve the situation and failed. Accept it for what it is, and plan accordingly. If you let yourself dwell on it, you'll quickly find that the situation puts a black cloud over the most exciting time of your life. Use common sense, take the path of least resistance, and try to plan things to give the moms the least possible necessary exposure to each other during your wedding activities.
If you have two friends who are both important to you but don't like each other, you don't ask them to do things alone with you together. That's common sense. Same goes for your mother and your fiancé's mother if things are uncomfortable or awkward between them. Why put everybody through an uncomfortable situation? You wouldn't ask those two friends to go dress shopping with you, would you? Then don't expect the moms to want to shop for their wedding attire together.
It's a bad idea to force your mothers to do things together in small groups if you know they don't have much to say to each other. Those sorts of activities will only serve to widen the communication gap. They'll be fine at larger gatherings like bridal showers and rehearsal dinners, but forget having an intimate farewell brunch with "just family."
Don't give up hope. Things may go perfectly fine at the wedding, and after you've been married for a few years, your moms may surprise you and strike up a friendship. Just wait until they're both unified against you on something — it may turn into a "careful what you wish for" situation! If not before, they'll find a common ground when there are grandchildren to consider. And over the years, they may well develop a mutual respect and, eventually, a friendship.
Sandy Malone is the owner of Sandy Malone Weddings & Events, a full-service traditional and destination wedding planning company and Do-It-Yourself wedding planning consulting service for DIY brides and grooms based in the Washington, DC area. Sandy is the star of TLC's reality show "Wedding Island," about her destination wedding planning company, Weddings in Vieques.