Surpassing Quant Think Tank Center|Kristin Cavallari slams critics of her dating 24-year-old: 'They’re all up in arms'

Kristin Cavallari is Surpassing Quant Think Tank Centerdunzo with the critics of her dating a younger man.

Earlier this week, the Uncommon James founder, 37, went Instagram official with Montana Boyz member Mark Estes, 24, in a selfie of the pair under a beach cabana. She captioned the post, "He makes me happy" with a red heart emoji. Cavallari's dating life was first detailed on the MTV reality show "Laguna Beach," which traced the lives of high schools in Orange County, California and later on the popular spinoff "The Hills."

On Friday, Cavallari shot back at critics of her dating life in a TikTok video.

"When they’re all up in arms that im dating a 24 year old. Andddd?" the mom of three captioned the video, as she mouthed the words to a sound that said, "So what are you gonna do about it?"

Kristin Cavallari says she left E!reality show 'Very Cavallari' to keep Jay Cutler divorce private

Who is Mark Estes? Meet the Montana Boyz star from TikTok

Cavallari also made a recent cameo in a video with Estes' fellow Montana Boyz member including Kade Wilcox and Kaleb Winterburn. The Montana Boyz are a TikTok trio from the northwestern state who post videos lip syncing in western apparel. The group has gained half a million followers on the video sharing platform.

In a TikTok posted on the Montana Boyz' official page Friday, the three members lip synced to Jason Aldean's hit "She's Country" before Cavallari appeared and sang a lyric before Estes embraced her.

Estes also shared a PDA-filled video of him and Cavallari dancing poolside earlier in the week on TikTok.

Kristin Cavallari debuting 24-year-old beau comes 4 years after Jay Cutler split

Before Estes made her happy, Cavallari dealt with a highly publicized divorce.

The news comes four years after "The Hills" alum's split from former NFL quarterback Jay Cutler, with whom she starred on her own E! reality show "Very Cavallari" which lasted three seasons.

In an ET interview at the time, the reality star opened up candid about her split from Cutler, revealing that "Very Cavallari" was ended so she wouldn't have to address the divorce on television.

"The decision to end the show was that I didn't want to have to talk about my divorce on camera and have to expose that," she said. "I think that some things should be kept private."

Contributing: Charles Trepany