She responded with actorly reflexes, offering an upturned chin, but making sure all the while to place her program discreetly over the seam of her pencil skirt, which was slit, in her view, a little too high for propriety.



She had risen before dawn to fly in from Vancouver, where she had been working 16-hour days filming “Emily Owens, M.D.,” her television series, which is scheduled for its premiere Oct. 16 on the CW network. But she showed no signs of fatigue, the only chink in her composure a perceptibly tightening smile.



“I’m a little off my game,” she said just as the first model glided down the runway. Under the circumstances, she had little choice, she said, but “to flip a switch and operate in a mode that’s almost preprogrammed.” And to turn on the charm. “You can’t be disgruntled, you can’t be belligerent,” she said. “It’s just not an option.”



It might have been an option a handful of years ago, when Ms. Gummer, with her younger sisters, Grace, an actress, and Louisa, a student, started to become fixtures on Manhattan’s society circuit, invited to film premieres, style-world festivities, store unveilings or, as fashion parlance would have it, the opening of an elevator. “I thought of those events as a lot of fun and treated them like a giant party,” Ms. Gummer said.



“Now I’m learning this is work.”



Like many of her peers in Hollywood, Ms. Gummer, 29, is acutely aware that in an image-obsessed culture, attaining a bankable profile is a 24/7 pursuit. It no longer suffices to snare eye-catching parts or turn up dutifully for the casting calls and after-theater parties, a ritual that was standard in her mother’s day. (Mom, for those who have been living in a yurt, is Meryl Streep. Dad is the sculptor Donald Gummer.)



“This whole idea of making appearances, it’s become a business,” Ms. Gummer said the next afternoon, sitting in a borrowed suite at the NoMad Hotel in the Flatiron district. “You’re vying for people’s focus and attention at a time when it seems anybody can get a little bit of fame.”



In the day of YouTube and Instagram, showing up at parties and showing off one’s style cred “is all part of the game,” said Bumble Ward, the executive vice president for publicity at 20th Century Fox. “It’s no longer, sadly, good enough to just be a brilliant actress. It’s not just about the movie, but what kind of double cuff is on your wrist.”



Being the daughter of a Hollywood legend isn’t the worst thing that can happen to an aspiring actress. But it can be a double-edged distinction, one that places Ms. Gummer in the company of ingénues like Lily Rabe, the daughter of Jill Clayburgh and the playwright David Rabe, or Zoe Kazan, whose grandfather was the director Elia Kazan, who find themselves dodging and courting the camera by turns.



“A lot of people in this business just want to be noticed,” Ms. Gummer said. “I spend a lot of time with my family trying not to be.”



The spotlight finds her just the same.



She is courted in part, she knows, because of her lineage. “It’s this,” Ms. Gummer said, fingers sliding down the Cleopatra nose, a ringer for Ms. Streep’s. “People get excited by this resemblance. They’re curious. It’s like meeting someone by proxy.”



During the last 12 months, Ms. Gummer, often accompanied by her sister Grace or her husband of one year, the actor Benjamin Walker (“Abraham Lincoln: Vampire Hunter”), has been paparazzi bait, photographed at a cluster of high-profile events.



She swept into the Vanity Fair Oscar party at the Sunset Tower in Los Angeles in February, hours after her mother had been awarded the Oscar for “The Iron Lady.” She appeared in a pearl gray Giles Deacon dress at the Metropolitan Museum of Art Costume Institute gala in May, her look earning her a coveted spot, if only for a night, on Vogue’s best-dressed list.



She was snapped in the same month with her sisters and Ms. Kazan at the Lincoln Center Institute Junior Spring Benefit on the terrace of the Bowery Hotel, an affair sponsored by Diane von Furstenberg. And in June she alighted on the High Line at a celebrity-seeded fund-raiser for the park, underwritten by Coach. She was paid to attend, Ms. Gummer said unabashedly: “Really, I wanted some rent money.” (A spokesman for Coach declined to comment.)