Her face then turns serious for a minute as she reflects on her firstborn, a child she lost 50 years ago and one she does not forget, even as her mind fades.
"She wasn't going to let the world pass her by."
Her other daughters came of age in a time unlike Denise's. Their world was more integrated. They reaped the benefits of their sister's sacrifice.
Kimberly McNair Brock is now married, 44, and serves as their mother's primary caretaker. She's also a chef focused on holistic nutrition.
Lisa, 48, is single and works for a nonprofit that uses animals to help people heal.
While they didn't feel they had to live their lives for the sister they lost, Kimberly says she felt like she was born without anonymity -- and with eyes trained on her.
"People knew about me before I got here," she says. "You were already measured before anyone gave you an opportunity to be who you were."
She also says she has gravitated to women about 17 years her senior, the same age Denise would have been if she was still alive -- an unconscious effort to fill a void.
The sisters feel a duty to honor Denise's legacy. They participate in Sojourn to the Past, a program that teaches high school students about the civil rights movement. They are also active in a scholarship fund established in the four girls' memory -- "giving people the chance to do what they couldn't," says Lisa.
What's more, they know it's on them to speak.
For most of their adult lives, their father, Chris McNair, served as the family spokesman. But the longtime county commissioner, now 87, was convicted in 2006 for accepting bribes and then suffered a stroke. He was recently released after serving two years in a federal prison medical facility.
Along the way, Lisa and Kimberly learned to step up. What happened to their sister, to their family, is a piece of American history they must own.
Even though they never knew Denise, it is the sisters' story to tell.
'More of a diplomat than me'
She could have had her own room after their older brother went off to college, but Dianne Robertson chose to stay put in the bedroom she shared with her little sister, Carole. The two, five years apart, would listen to the radio at night. It was the late 1950s, and rock 'n' roll had taken hold.
"She knew all the songs," Dianne says. "'In the Still of the Night,' she really liked that one."
Outside, Carole often tagged along with Dianne and her friends. At the movie theater, the younger girl would look on in horror as Dianne and the others got into what she calls "all sorts of devilment" -- like tossing ice and popcorn from the upper balcony, where blacks were relegated, onto the white folks below. When their boyfriends would put their arms around the teenage girls, Carole would gasp and say, "I'm gonna tell Mama!"
"That's what we all remember. She was everyone's little sister," Dianne says. "We'd have to bribe her to not tell our parents."
The Robertsons, both educators, groomed their children to achieve. The family lived in a tight-knit community rich with black role models: business owners, lawyers, doctors, preachers and teachers. On Sundays, after dinner, the family would go on drives and admire the big, beautiful homes in white-only neighborhoods. Going to college and shooting for dreams was a given.
But where they came from was far from perfect. Their neighborhood in Birmingham was dubbed "Dynamite Hill" because there were so many explosions. Her parents shielded them from much of the ugliness. The kids were never allowed out at night alone. Rather than letting them take buses, where they'd feel the indignity of sitting in the back, their parents insisted on driving them.