Kourtney Kardashian didn't hold back her true feelings when she saw Kim Kardashian's Thierry Mugler mini dress

Kim Kardashian West was not pleased with sister Kourtney Kardashian on Sunday night’s episode of Keeping Up with the Kardashians.

During one scene, Kim, 38, Facetimed Kourtney, 40, to give her a preview of the curve-hugging turquoise Thierry Mugler mini dress that she planed to wear to the 2019 Met Gala afterparty.

“What is this for?” Kourtney asked Kim.

Kim jokingly replied by saying: “I was thinking of wearing this to your 40th birthday party. What do you think?”

“No,” her sister blatantly answered.

Kim Kardashian
Credit: E!/Keeping Up with the Kardashians

Kim explained that she was working with the Mugler team on altering the dress a bit, but Kourtney still wasn’t loving the look. “So this will be all beaded obviously and all crystals,” the KKW Beauty mogul said.

“Are you coming as Nicki Minaj?” the Poosh founder asked.

“This is Cher honey,” Kim answered.

Kourtney fired back by saying: “I would say, is it October 31st?”

“Don’t insult me!” Kim replied.

Kim Kardashian, Kourtney Kardashian
Credit: E!/Keeping Up with the Kardashians

In a confessional interview during the episode, Kim explained how embarrassed she was by Kourtney’s reaction, because the entire Mugler design team was in the room during their Facetime call.

“I have been planning my Met look since last year and she was just so rude in front of the whole Mugler team. ‘Ew! Oh my god. Is this Halloween?'” Kim said, mimicking her sister. “It’s all super embarrassing and I can’t even stomach it.”

Kim Kardashian
Credit: E!/Keeping Up with the Kardashians

After Kim ended the call with Kourtney, designer Manfred Thierry Mugler’s manager, Jean-Baptiste Rougeot, told the star he was surprised by Kourtney’s dislike of the design.

“I should show you the email I got. So I received an email from Dani [Michelle, Kourtney’s stylist]. Really like flattering Mr. Mugler saying, ‘I know how much you work well with Kim,'” he said.

Kim Kardashian West
Credit: Erik Pendzich/REX/Shutterstock

That angered Kim even more. “Manfred Thierry Mugler’s manager let us know that, ‘Oh that’s so weird she doesn’t get this vibe, because she’s the one that’s hitting us up wanting looks.’ And we’re like, ‘What?'” Kim said. “For her to not only try to use the same designer but then to be so rude, it really hit me the wrong way.”

Later on in the same episode of KUWTK, Kim explained that she works hard to maintain close relationships with the designers she borrows dresses from, and she doesn’t think Kourtney appreciates that.

“I don’t think Kourtney understands the legwork behind this. I don’t think anybody understands. You have to really have a relationship with that designer. She has no idea how this works,” she said.

Kourtney defended herself and her stylist, who has requested dresses from designers that Kim also works with. “We have completely different looks. I’m not trying to copy your styles. But on a same designer, you can’t ban me from [them],” she said.

Kim fired back saying: “They said, ‘Sorry, Kourtney’s stylist pulled everything.’”

But by the end of the episode, Kim extended an olive branch to Kourtney by giving her a one-of-a-kind Versace dress designed by the late Gianni Versace to wear to her 40th birthday party.

“Kourtney is really emotional these days and going through it,” Kim said. “I’m still really upset with her and the stylist, but it’s not the time. I want her to look amazing.”

Keeping Up with the Kardashians airs Sundays at 9 p.m. ET/PT on E!.