By Tierney McAfee and Tara Fowler, People

Barbara Bush shared the secret to aging gracefully in an interview with granddaughter Jenna Bush Hager on the Today show.

“You’re known for your pearls,” Jenna remarked to Barbara, who turns 90 on Monday.

“The pearls are to cover the wrinkles, which they no longer do,” she said. “You can’t wear pearls all over your face.”

And as for why she never dyed her distinctive white hair? “I wanted to play golf, I wanted to play tennis, I wanted to swim. And my hair turned, as I’m sure someone else will tell you, orange, green, yellow, depending upon how much chlorine in the pool. So I decided to go white.”

Barbara is celebrating her 90th birthday in style, with the re-release of her 1994 memoir, which features gushing new forewords from each of her five children.

In his foreword for Barbara Bush: A Memoir, the Bush matriarch’s oldest son, former President George W. Bush, describes her as a fearless, quick-witted woman who taught her children how to “love, love, and laugh.”

“Mom has a sharp and quick wit. She is not afraid to speak her mind. She is self-deprecating,” he writes. “She can spot a phony before most. She deflated the pompous and arrogant. She is a pro at putting people at ease because she herself is at ease.”

George’s younger brother, former Florida governor Jeb Bush, praises Barbara as a “national treasure” who taught him how to be a good parent and instilled in him a love of reading.

He also reveals one of her family nicknames: “the Enforcer.”

“God help you if she ever caught you acting arrogant,” Jeb writes in his foreword. “You would get that Barbara Bush look and then you would be hit with her very quick and sharp wit that would put you in your place.”

Barbara laughed at this nickname when Jenna brought it up in their interview. “If you do something bad, I point it out to you,” she said.

But she’s also quick to defend her family. “I stood up for you when you stuck your tongue out at all the press,” she pointed out to Jenna.

Barbara also lifted her children up in their times of need. Her son Neil Bush explains how she helped him when he struggled with reading in elementary and middle school.

“Mom felt my pain and worked hard to find a diagnosis and solution. She stood by me, lifted my spirits, helped me find joy in things I did well, and made sure my life wasn’t mired in self-doubt,” he writes.

After Neil was diagnosed with dyslexia, the then-First Lady created the Barbara Bush Foundation for Family Literacy, a nonprofit organization that advocates for literacy in homes across America. Barbara still does work for the foundation, which is holding a special Celebration of Reading event on Monday in honor of her 90th birthday.

The former First Lady’s love of literature is surpassed only by her love for her children and her husband, former president George H.W. Bush, who celebrated his own 90th birthday on June 12, 2014, by making a tandem parachute jump out of a helicopter.

“I could hardly breathe, I thought he was so beautiful,” she told Jenna of the first time she laid eyes on her future husband.

Several of the Bush children write about their parents’ 70-year marriage and undying devotion to each other in their forewords to her book.

“No doubt her number one love was Dad,” George W. Bush writes in his foreword, calling his father “the love of [his mother’s] life.”

Barbara’s youngest son, Marvin Bush, writes, “Growing up, we had a front row seat at one of the greatest love stories that ever existed. My parents can’t get enough of each other. Their love has grown stronger with each passing year. They laugh at each other’s goofy jokes, hold hands when no one is around, and generally look at each other like teenagers in love.”

Barbara’s only daughter, Doro Bush, adds that these days, her mother is dedicated to caring for her husband, who is now confined to a wheelchair due to Parkinson’s disease.

“While his memory is fading, his love of others, especially my mom, is powerful,” Doro writes, “and Mom does everything she can to color his world.”

Barbara’s memoir was re-released on May 26. All proceeds from the book are donated to the Barbara Bush Foundation for Family Literacy.