The Supporting Sunny Group had planned this luncheon carefully. Because Sunny Harper-Owen, their longtime friend, warmly remembered the years she spent in Paris, the group had decided on a French theme and were bringing quiche, onion soup and chocolate mousse.

More important, they’d developed strategies to avoid confusing the guest of honor. The six women would arrive at the home of the hostess one at a time, so that each could greet Ms. Harper-Owen individually. They’d encourage her to reminisce about attending the Sorbonne and taking cooking classes, because she finds it easier to remember what happened long ago than last month.

“Let’s try to keep the conversation limited to one person talking at a time,” Marian Karpisek had reminded the others in an e-mail before the lunch. “Make sure that Sunny is included in the conversation by looking at her as well as at the rest of us, and giving her time to reply and interact as she wants.”

They all live in San Diego and range in age from 52 to 76. Most met more than 15 years ago, through a monthly spiritual gathering called the Women of Ancient Wisdom. So her friends were in a position to take notice when, two years ago, Ms. Harper-Owen was faltering.

When her turn came to plan the monthly program, “she couldn’t do it at all,” Ms. Karpisek, the group’s elder, told me on the morning of the French lunch. “She couldn’t focus.” Increasingly, “she’d have trouble finding words and completing thoughts.” She began to withdraw from conversations.

“We said, something is really wrong here,” said Ms. Karpisek, who gathered the group to discuss how to help their friend, a talented jewelry maker and dedicated volunteer who was only 64. “We didn’t want to lose her. We wanted to be part of her life.”

Christening themselves the SSG, the women researched Ms. Harper-Owen’s symptoms and sent a trusted emissary to her husband, Wally Owen, to urge him to pursue neurological testing. The eventual diagnosis: early-onset Alzheimer’s disease.

Friendships often fade or collapse at this point. Alzheimer’s is gaining on cancer as the most feared disease. Even when people don’t want to turn away, they don’t know how to preserve relationships with those who can’t easily maintain a conversation or recall a shared past. Family members are expected to step up, but friends can slip away.

The SSG members decided, instead, that each week one of them would spend time with their friend. They’re passing along their experiences here in hopes that others will organize themselves to sustain friendships with people developing dementia.

It took some trial and error to find activities that worked. Visits or excursions can’t require more than a few hours, or Ms. Harper-Owen will tire. “Anything that causes her to feel anxious — crowds, noise, a lot of strangers — that isn’t conducive to her enjoying herself,” Ms. Karpisek said. She once took Ms. Harper-Owen to see “Midnight in Paris” — the French idea, again — but the time-traveling plot proved difficult to follow.

Now, every sixth week, Ms. Karpisek takes her to a nail salon, where they both have manicures and pedicures. With Nere Lartitegui, Ms. Harper-Owen watches — and sings along with — old movie musicals like “South Pacific” or (of course) “Gigi.” Jean Stein drives her to a favorite beach, where they sit on a bench, drink smoothies and watch the pelicans. Ms. Harper-Owen likes visiting the quiet meditation garden in Encinitas.

Afterward, SSG members circulate an e-mail describing the day and their friend’s response, to help guide the others. Ms. Harper-Owen’s husband and their son, Dan, get copies, too.

Dementia progresses, so “what worked in the beginning doesn’t work as well anymore,” Ms. Karpisek said. Despite multiple reminders about each SSG excursion, for instance, one member rang the doorbell recently to find that Ms. Harper-Owen had forgotten and was still in bed.

Some day, members know from their ongoing research, she will have trouble walking to the beach or choosing a nail color. “It will come to the point where she doesn’t know any of us,” Ms. Karpisek said. But the SSG will still visit her, members have vowed.

For now, though, she still looks forward to their outings, to their presence. I know, because after the French lunch — which Ms. Karpisek declared one of the best SSG events ever — I talked with a grateful Wally Owen and then with his wife, now nearly 67 and still quite able to speak for herself.

“It was fabulous,” Ms. Harper-Owen said of the lunch. “To be with my friends, my dear sweet people. To hang out and have great food — onion soup and some lovely pâté — and a little wine. So wonderful.”

She feels very lucky, she told me. “I’m so appreciative of what they’re doing, these amazing, wonderful women coming together.”

Paula Span is the author of “When the Time Comes: Families With Aging Parents Share Their Struggles and Solutions.”