August 5, 2021 | 1:09pm

Are diamonds really a girl’s best friend? Maybe not, if that girl is Nicky Hilton.

The younger socialite sister, 37, once staged her own Bling Ring when she borrowed diamonds from mom Kathy Hilton without asking — sending the “Real Housewives of Beverly Hills” star, 62, into a tailspin over the suspected theft.

“One of my funniest memories of borrowing something from my mom’s closet was when I was in my 20s and I had just landed from Miami,” Nicky told Footwear News for their August cover story.

“I ran into [my mom’s] closet and sort of threw something together last minute.” 

After nabbing a vintage Valentino skirt and Tom Ford-designed Gucci heels from her mother’s extensive wardrobe, Nicky was searching for a high-fashion pièce de résistance.

“I needed to be, like, glammed up, so I just went in and I throw on a necklace and I was out the door,” she said. “Within an hour she’s calling me, panicking.”

The socialite quickly realized she’d left chaos in her wake, as her mother called security to track down the missing bling.

“She has the entire Waldorf Astoria security team looking at the cameras,” she continued. “Apparently, this necklace that I had borrowed is extremely valuable and she thought it was stolen”

Paris, Kathy and Nicky Hilton
One fashionable family: Paris and Nicky Hilton borrow pieces from their mom Kathy’s closet.
Getty Images

And it seems Nicky’s sticky fingers haven’t gone away with age; she recently caused confusion by borrowing one of Kathy’s Hermès Kelly bags without asking.

“I came home from Paris and I went quickly to look and check on my things and I said, ‘Where is my little pink purse?!” the “RHOBH” recalled during the FN shoot. “I thought, ‘Wait a minute, call Nicky.’…‘Do you have your mother’s pink purse?’ ‘Yes I do.’”

It seems things are now hunky-dory between Kathy and her two daughters, and she even admitted to buying a velvet Yves Saint Laurent cape thinking Nicky and Paris, 40, would “probably wanna borrow” the distinctive design.

It’s easy to see why the sisters raid their mother’s closet, as the boutique-style space includes designer duds from brands like Chanel, Oscar de la Renta and Valentino. 

But while the cavernous closet is filled with fashion, don’t expect to find plastic footwear in there anytime soon. When Paris told FN she dislikes Crocs, Kathy replied, “What’s Crocs?”