Kathy Hilton responds to criticism of Kim Kardashian's casual outfit at her Christmas party: “That's silly”

Kevin Ostajewski From left: Paris Hilton, Kris Jenner, Kathy Hilton, Kim Kardashian and Nicky Hilton Rothschild

Kathy Hilton is a fan of Kim Kardashian's holiday fashion choices.

When asked by TMZ about fans who “ripped” Kim, 42, for the casual rocker look she wore to the Hilton family Christmas party – high-waisted Dolce & Gabbana leather pants with a belt and a vintage “Up in Smoke” tour concert T-shirt tucked into her bra – Kathy said, “That's silly, that's ridiculous.”

“Everyone is simply [supposed] come as they want and feel comfortable,” the 63-year-old celebrity continued when the outlet asked if there was a theme for the evening.

When asked if she found anything “wrong” with the SKIMS founder's unusual ensemble, Kathy replied: “No, no. She always looks beautiful.”

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Kevin Ostajewski From left: Paris Hilton, Kris Jenner, Kathy Hilton, Kim Kardashian and Nicky Hilton Rothschild

RELATED: Kim Kardashian wears brown hair again for her family's Christmas party: “We're back”

Childhood friends Kim and Paris, 41, reunited for a star-studded Christmas party over the weekend of December 17, posting photos on social media from the holiday bash – which was also attended by Kris Jenner, Paula Abdul, Heidi Klum, Paris' husband Carter Reum and her sister Nicky Hilton Rothschild.

For the event, Paris wore a red lace minidress and sparkly silver Mary Jane pumps, while younger sister Nicky, 39, opted for a floral minidress. Kathy wore a festive red checked dress with a large red bow on the bodice and Kris, 67, rocked a patterned black pantsuit.

Alongside the BFF photo taken in front of a white Christmas tree, Paris posted a family photo with Nicky, Kathy and her father Rick Hilton, a photo with her tuxedo-clad husband and a shot of herself DJing with Abdul, 60.

“My mom always throws the most iconic parties,” Paris wrote on her Instagram page, sharing a series of festive snaps from the party. “I loved celebrating the holidays with family and friends this weekend. What are your favorite traditions this time of year? #Slivmas.”

Kevin Ostajewski Paris Hilton and Kim Kardashian

RELATED: Paris Hilton shares throwback photos with mother Kathy and sister Nicky in matching Christmas dresses

Later, Kim attended the Kardashian-Jenner family's annual Christmas Eve party – which this year was enhanced by an appearance from Sia!

The mogul returned to her brunette roots for the occasion, wearing a sparkling silver chainmail dress.

The party took place at Kourtney Kardashian's home in Calabasas, California, and also included red Christmas trees, lots of chocolate treats, an all-red ball pit for the kids, and a few songs from Sia herself.

Kim Kardashian/Instagram

In videos shared by some family members, the 47-year-old Australian musician can be seen singing alongside Kim's 9-year-old daughter North in what appears to be a giant makeshift gift box.

RELATED: Kim Kardashian Has Brown Hair Again for Her Family's Christmas Party: 'We're Back'

Kim Kardashian/Instagram

During their joint performances, Sia and North sang their song “Snowman” as well as their 2014 hit “Chandelier.” The nine-time Grammy nominee wore an all-white ensemble, while North opted for a shiny two-piece.