You Won't Believe What Sets Dorinda Medley Off on The Real Housewives of New York City

Luann de Lesseps had no idea what was coming her way when she insulted a birthday cake in this clip from the Bravo hit's next episode

Note to self: Do not ever, under any circumstances, talk trash about Dorinda Medley's birthday cake.

In this sneak peek of next week's all-new episode of The Real Housewives of Beverly Hills, the action's right where we left it at Dorinda's Berkshires home—and things are about to go from bad to worse. It's clear that last night's cliffhanger argument between Bethenny Frankel and Luann de Lesseps broke the party into two groups, with Luann and Ramona Singer camped out in the kitchen. Luann's still losing her mind over Sonja Morgan's rescinded invitation, loudly questioning why there would be a cake that says "Happy Birthday, Dorinda" if the reason for the trip wasn't, as her host claimed, to celebrate a birthday?

Her big mistake? Continuing to rant once Ms. Medley herself was within earshot.

"You can talk about me, you can talk about my house, you can talk about my decorations—but do not mess with Diane Sincala's birthday cake," Dorinda says calmly in one of her talking heads. "When it comes to my mother, you don't go there."

That calm, however, is nowhere to be found in the moment. When Dorinda enters that kitchen, Luann never knew what hit her.

"Don't say my 'non-birthday birthday.' It's not my birthday. My mother bought this on Saturday," she begins, growing more and more agitated with each sentence. "Don't say that. I think everyone is acting very poorly. I put in a big effort here and this is my home. And I made a conscious choice not to invite Sonja so we could all have a good time! And I think it's a disgrace of you people!"

And the fun doesn't stop there. To see Dorinda really let 'em have it, press play on that video above.

Dorinda's epic meltdown isn't the only thing to look forward to (or fear) in next week's episode. We'll also see the explosive conclusion of that fight between Bethenny and Luann and, though they seem to be on the same team in the clip, Luann will also hear from Ramona on how the Pinot Queen thinks the Countess broke girl code over Tom. Meanwhile, Jules Wainstein's first weekend away with the girls takes a turn—and things were going so well!—when she's confronted with a family emergency.

The Real Housewives of New York City airs Wednesdays at 9 p.m. on Bravo.