“I want to show people the regularity of my life, and that not everything is so fancy,” she said.

Her fans can’t get enough. “If you’re not following Beyoncé’s mom on Instagram, here’s what you’re missing,” declared an article from Harper’s Bazaar in August. “She’s basically everybody’s auntie who is a sweetheart, but still keeps it real when necessary,” said Crissle West, a co-host of “The Read,” a popular podcast on hip-hop and pop culture.

Daughter of a Seamstress

Ms. Lawson, nee Celestine Ann Beyincé, grew up in the 1950s in “a real small town” in Galveston, Tex. The last of seven siblings, her father was a longshoreman and her mother was a seamstress. She picked up dressmaking at a young age, creating sparkly stage outfits for her Supremes-inspired singing group while in high school.

At 19, she moved to California to work as a makeup artist for Shiseido Cosmetics (she learned styling tricks from drag queens, she said) but returned to Texas a year later when her parents fell ill. With help from her then-husband, Matthew Knowles, a former Xerox executive, she opened a 12-seat hair salon in Houston called Headliners. The salon, which had more than a two-decade run, helped the Knowles family afford an upper-class lifestyle.

It was also an impromptu stage for her young brood, while women under dryers acted as judges.

When Destiny’s Child, the girl group whose most famous lineup consisted of Beyoncé, Kelly Rowland (“my other daughter”) and Michelle Williams, began to break out in the late 1990s, Ms. Lawson returned to dressmaking and whipped up matching cutaway Boy Scout uniforms, barely-there camouflage hot pants and Tarzan-like fur sheaths for the group to wear onstage.

As Beyoncé put it in her Council of Fashion Designers of America speech last year, designers were reluctant to dress “black country curvy girls,” so her mother stepped in. “They looked a little crazy sometimes,” Ms. Lawson said, “but people always wondered what they were going to wear next.”

The “Bootylicious” touch helped the group stand out. Destiny’s Child went on to sell over 60 million records worldwide, and Destiny’s mother became a fashion force. In 2004, she and Beyoncé started the House of Deréon, a trendy, low-priced clothing brand named after Ms. Lawson’s mother. A juniors collection, bedding and a clothing line aimed at older women called Miss Tina soon followed.