Brooke Shields Says Daughter Grier, 15, Loves Swiping Designer Labels from Her Closet

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As the mother of two teenage daughters, Brooke Shields is used to items mysteriously going missing from her closet. And most often, it's her youngest daughter, 15-year-old Grier Hammond Henchy who snatched something.

"My younger [daughter] is extremely into fashion," Shields, 56, tells PEOPLE at Marie Claire's Power Trip: Off the Grid sponsored by United Explorer Card, Mercedes-Benz and Miraval Berkshires Resort & Spa.

"If I want to know where anything good that I have is, and I can't find it in my closet, I know exactly where to find it," the star jokes. "It's her!"

Shields, who shared a sweet style moment with Grier in Sept. by attending Ferragamo's Milan Fashion Week together, says her daughter tends to give a sly response when she asks where her missing clothes went.

"And she's [like], 'Oh, I forgot to give that back to you.' I'm like, 'You also forgot to ask me to borrow it. So let's go back, back up a bit,'" Shields says.

While Grier tends to "only" gravitate toward the designer pieces in Shields' closet, the actress' eldest daughter, Rowan Francis Henchy, 18, whom she also shares with husband Chris Henchy, doesn't do the same.

RELATED: Brooke Shields Gets Emotional as She Sends Daughter Rowan Off to College: 'So Proud of You'

"[Grier's] just a little bit of a label monger," Shields says. "The other one is not at all. [Rowan]'s like, 'Mom, it doesn't matter to me.' They're completely the opposite."

Allie Holloway

RELATED: Brooke Shields Shares Photo and Videos from Daughter Rowan's High School Graduation: 'My Baby Girl'

Although Rowan doesn't snag Shields' personal pieces from her wardrobe as often, she did pull out one of her mom's famous red carpet gowns to wear to prom last spring.

The Blue Lagoon actress shared a photo of herself and daughter Rowan looking stunning in the strapless red gown her mother originally wore to the 1998 Golden Globes. It was the year Shields earned her second nomination for her NBC sitcom Suddenly Susan. Rowan completed her prom look with a black Hermés Constance shoulder bag.

Brooke Shields/Instagram

"I thought it was a special night when I was nominated for a Golden Globe and wore this dress in 1998, but nothing could have prepared me to see my daughter wearing it to her prom," Shields wrote in an Instagram caption. "Proud mama!"

During Shields' visit to the "Power Trip: Off the Grid" conference, which gathered business leaders to collaborate and inspire for 36 hours, the star joined Marie Claire Editor in Chief Sally Holmes for an empowering conversation about ageism, female friendships and more.

Allie Holloway Brooke Shields and Sally Holmes

The actress also opened up about her new wellbeing brand, Beginning Is Now, which she had the idea for when she realized the lack of representation she felt in her demographic. "I remember saying, 'I'm fitter. I'm stronger. I kind of don't give a s—t in the same way. I know who I want to have around me as people. I've raised children. I've had a whole career multiple times. I've done all these things, and now I'm being told 'Oh, well, you're over. Your ovaries don't work anymore, so you're good. Or you've done all that, so why don't you just take a break and relax?' I feel as if I'm just beginning."

Instead, she said she wants to celebrate women as they get older. "I'm the conduit. I'm not the guru. I'm the ring leader, the connector. And I'm just the face that gets people to talk to each other. This is less about me and more about us. The response has been extraordinary, and now we're going into different categories. We're going into beauty and we'll be going into other categories as well."