"She led her own fascinating life and didn't meddle in ours," Carole writes of her "remarkable" mother-in-law, Lee

Editor’s note: Former Real Housewives of New York City star Carole Radziwill, who married Lee Radziwill’s son, Anthony, in 1994 and lost him to cancer five years later, remembers her one-of-a-kind mother-in-law, who died this week at 85. For more on Lee’s amazing life, subscribe now to PEOPLE or pick up this week’s issue, on newsstands Friday.

I met Lee 30 years ago, at her home in East Hampton. I was dating her son and it was time to meet his mother. She was one of the most interesting women of her day. A princess, a startling beauty, a world traveler.

Get push notifications with news, features and more.

During my marriage, we enjoyed dinners, holidays and summer weekends together. She adored her son but instinctively knew her place. She led her own fascinating life and didn’t meddle in ours.

When Anthony was diagnosed with cancer, our relationship shifted; I was strong and in charge and she was going through unimaginable pain. We became allies.

Image zoom Laura Cavanaugh/Getty

After we buried Anthony, we clung to each other in grief. Neither of us knew how to navigate it. Then Lee moved to Paris, as I drifted in New York — both of us trying to go on. Sometimes in moving on, you let go of everything. There were gaps. But over time we closed them.

In the 20 years after Anthony’s death, Lee always referred to me as her daughter-in-law. We fell into a comfortable routine of casual dinners, sometimes a movie. Dinners were always the same: her apartment, at a small card table in her living room with a silk scarf tablecloth. Set perfectly, minimally, for two.

Image zoom Lee Radziwill in 1967 Reg Burkett/Express/Getty Images

Image zoom Lee Radziwill (left) and Carole Radiziwill in 1999 Ed Betz/AP/REX/Shutterstock

Talk was easy even when we hadn’t seen each other in months. Lee was an insatiable reader, she knew all the latest art exhibits, books and plays. She could tell you the new designers from Paris to New York and which would have longevity. She was fluent in Spanish and French and moved between cultures and language like a ballerina.

It seems we barely knew each other when I was married but kept our sights on one another, and then I was gifted with a lovely friendship with a remarkable woman. She was an original, loved by many.

The fascinating woman I met all those years ago was frail in her 80s, but with the same cheekbones, same chiseled beauty, same eager curiosity and fluid ease with any subject you could dream up. She was warm but strong-willed, both formidable and playful. She still had a razor-sharp wit and intellect.

She didn’t set trends, she defined style. She expected authenticity and lived unapologetically.