For months, editors at People magazine had been zeroing in on Betty White for an end-of-year cover article. Her 100th birthday was coming up on Jan. 17, and readers always seemed to warm to her self-deprecating, slightly naughty observations. As the toast of social media in recent years, Ms. White appealed to old and young.

By mid-December, Liz McNeil, a 29-year-veteran of the magazine, and a new colleague, Dory Jackson, were collaborating on the piece, with Ms. White responding to questions via email, according to Wendy Naugle, People’s deputy editor. On Dec. 23, editors closed the issue. It hit newsstands on Wednesday and began arriving in subscriber mailboxes on Friday.

Next to a glossy photograph of Ms. White, her eyes twinkling, the People trumpets sounded: “Betty White Turns 100!”

Ms. White died on Friday morning. She was 99.

As tributes began to wash across Twitter, with fans celebrating Ms. White’s comedic performances on “The Golden Girls” and “The Mary Tyler Moore Show,” People also began to trend. Some fans blamed the magazine for jinxing Ms. White. (In addition to its weekly issue, People also marked her impending centennial with a commemorative issue entirely devoted to her seven-decade career.)

Others were pleased that Ms. White, known for her devilish sense of humor and impeccable comedic timing, had seemed to have pulled off one last laugh.

Dan Wakeford, People’s editor, was in London when he got the word that Ms. White had died, turning his cover into a Hall of Fame example of the risk of reporting something that hasn’t quite happened yet. (The most infamous example remains the Chicago Daily Tribune’s decision in 1948 to mistakenly announce that “Dewey Defeats Truman.”)

Perhaps adding insult to injury, a competing celebrity news outlet, TMZ.com, broke the news of Ms. White’s death, citing anonymous law enforcement sources.

Still, People was able to get the first official confirmation — from her agent, Jeff Witjas, who had helped arrange the interview. “Even though Betty was about to be 100, I thought she would live forever,” Mr. Witjas told the magazine. “I will miss her terribly and so will the animal world that she loved so much.”

People then posted a comment from Mr. Wakeford on its Twitter account. “We are deeply saddened by the news of Betty White’s passing,” he said. “We are honored that she recently chose to work with People to celebrate her extraordinary life and career.”

Speaking by phone, Ms. Naugle said she and other staffers were “all in shock.” Ms. White, she noted, on Tuesday had shared an image of her 100th-birthday cover with her 1.3 million Twitter followers. “People Magazine is celebrating with me!” the post read.

It turned out to be Ms. White’s last post. In one from Dec. 15, she promoted a documentary, “Betty White: 100 Years Young,” which was scheduled to be shown in theaters on Jan. 17. “I’m going BIG for my birthday — right to the BIG SCREEN!” Ms. White had said.

The film’s producers, Steve Boettcher and Mike Trinklein, said the film will come out as scheduled. “Betty always said she was the ‘luckiest broad on two feet’ to have had a career as long as she did,” they said in a statement. “And honestly, we were the lucky ones to have had her for so long.”

Asked to reconcile the sadness of Ms. White’s death with the whoops of the cover, Ms. Naugle looked on the bright side. “I think fans will be touched to know that she was funny and in good spirits right until the end,” she said.

Ms. White had quipped to People, for instance, that her longevity could be attributed, in part, to her diet. “I try to avoid anything green,” she said. “I think it’s working.”