Phillips died Wednesday in Minneapolis after a long battle with Alzheimer's disease, said Gene Willis, a publicist for the Universal Uclick syndicate.
"My mother leaves very big high heels to fill with a legacy of compassion, commitment and positive social change," her daughter, Jeanne Phillips, who now writes the column, said in a statement.
Private funeral services were held Thursday, Willis said.
The long-running "Dear Abby" column first appeared in the San Francisco Chronicle in 1956. Mother and daughter started sharing the byline in 2000, and Jeanne Phillips took over in 2002, when the family announced Pauline Phillips had Alzheimer's disease.
Pauline Phillips wrote under the name Abigail Van Buren. Her column competed for decades with the advice of Ann Landers, written by her twin sister, Esther Friedman Lederer, who died in 2002. Their relationship was stormy in their early adult years, but they later regained the closeness they had growing up in Sioux City, Iowa.
The two columns differed in style. Ann Landers responded to questioners with homey, detailed advice. Abby's replies were often flippant and occasionally risqué one-liners, like some of those collected for her 1981 book "The Best of Dear Abby."
Dear Abby: My boyfriend is going to be 20 years old next month. I'd like to give him something nice for his birthday. What do you think he'd like? - Carol
Dear Carol: Nevermind what he'd like, give him a tie.
Dear Abby: What inspires you most to write? - Ted
Dear Ted: The Bureau of Internal Revenue.
Dear Abby: I've been going with this girl for a year. How can I get her to say yes? - Don
Dear Don: What's the question?
Phillips admitted that her advice changed over the years. When she started writing the column, she was reluctant to advocate divorce:
"I always thought that marriage should be forever," she explained. "I found out through my readers that sometimes the best thing they can do is part. If a man or woman is a constant cheater, the situation can be intolerable. Especially if they have children. When kids see parents fighting, or even sniping at each other, I think it is terribly damaging."
She willingly expressed views that she realized would bring protests. In a 1998 interview she remarked: "Whenever I say a kind word about gays, I hear from people, and some of them are damn mad. People throw Leviticus, Deuteronomy and other parts of the Bible to me. It doesn't bother me. I've always been compassionate toward gay people."
If the letters sounded suicidal, she took a personal approach: "I'll call them. I say, 'This is Abby. How are you feeling? You sounded awfully low.' And they say, 'You're calling me?' After they start talking, you can suggest that they get professional help."
In a time before confessional talk shows and the nothing-is-too-private culture of the Internet, the sisters' columns offered a rare window into Americans' private lives and a forum for discussing marriage, sex and the swiftly changing mores of the 1950s, '60s and '70s.
Asked about Viagra, Phillips replied: "It's wonderful. Men who can't perform feel less than manly, and Viagra takes them right off the spot."
About working mothers: "I think it's good to have a woman work if she wants to and doesn't leave her children unattended - if she has a reliable person to care for them. Kids still need someone to watch them until they are mature enough to make responsible decisions."
One trend Phillips adamantly opposed: children having sex as early as 12 years old.
"Kids grow up awfully fast these days," she said. "You should try to have a good relationship with your kids, no matter what they do."
Pauline Esther Friedman, known as Popo, was born on Independence Day 1918 in Sioux City, Iowa, 17 minutes after her identical twin, Esther Pauline (Eppie). Their father was a well-off owner of a movie theater chain. Their mother took care of the home. Both were immigrants from Russia who had fled their native land in 1905 because of the persecution of Jews.
"My parents came with nothing. They all came with nothing," Phillips said in a 1986 Associated Press interview. She recalled that her parents always remembered seeing the Statue of Liberty: "It's amazing the impact the lady of the harbor had on them. They always held her dear, all their lives."
The twins spent their growing-up years together. They dressed alike, both played the violin and both wrote gossip columns for their high school and college newspapers. They attended Morningside College in Sioux City.
Two days before their 21st birthday, they had a double wedding. Pauline married Morton Phillips, a businessman, Esther married Jules Lederer, a business executive and later founder of Budget Rent-a-Car. The twins' lives diverged as they followed their husbands to different cities.
The Phillipses lived in Minneapolis, Eau Claire, Wis., and San Francisco, and had a son and daughter, Edward Jay and Jeanne. Esther lived in Chicago, had a daughter, Margo, and in 1955 got a job writing an advice column. She adopted its existing name, Ann Landers.
Pauline, who had been working for philanthropies and the Democratic Party, followed her sister's lead, though she insisted it wasn't the reason for her decision. She arranged for an interview with an editor of the San Francisco Chronicle and presented sample columns, arguing that the paper's lovelorn column was boring. The editors admired her breezy style, and she was hired.
Searching for a name for the column, Pauline chose Abigail from the Bible and Van Buren from the eighth American president. Within a year she signed a 10-year contract with the McNaught Syndicate, which spread her column across the country.
"I was cocky," she admitted in 1998. "My contemporaries would come to me for advice. I got that from my mother: the ability to listen and to help other people with their problems. I also got Daddy's sense of humor."
Pauline applied for the advice column without notifying her sister, and that reportedly resulted in bad feelings. For a long time they did not speak to each other, but their differences were eventually patched up. In 2001, the twins, then 83, attended the 90th birthday party in Omaha, Neb., of their sister Helen Brodkey.
The advice business extended to the second generation of the Friedmans. Not only did Jeanne Phillips take over "Dear Abby," but Esther Lederer's daughter, Margo Howard, wrote an advice column for the online magazine Slate.
Aside from the Dear Abby column, which appeared in 1,000 newspapers as far off as Brazil and Thailand, Phillips conducted a radio version of "Dear Abby" from 1963 to 1975 and wrote best-selling books about her life and advice.
In her book "The Best of Abby," Phillips commented that her years writing the column "have been fulfilling, exciting and incredibly rewarding. ... My readers have told me that they've learned from me. But it's the other way around. I've learned from them. Has it been a lot of work? Not really. It's only work if you'd rather be doing something else."
Associated Press writer Bob Thomas in Los Angeles contributed to this report.