Valerie Harper, who scored guffaws and stole hearts as Rhoda Morgenstern on back-to-back hit sitcoms in the 1970s, has died. She was 80.

Longtime family friend Dan Watt confirmed Harper died Friday, adding the family wasn't immediately releasing any further details.

Harper was a breakout star playing the lovable sidekick on The Mary Tyler Moore Show, then as the funny leading lady of the spinoff series, Rhoda.

She won three consecutive Emmys (1971-73) as supporting actress on The Mary Tyler Moore Show and another for outstanding lead actress for Rhoda, which ran from 1974-78. Beyond awards, she was immortalized — and typecast — for playing one of television's most beloved characters, a best friend the equal of Ethel Mertz and Ed Norton in TV's sidekick pantheon.

Fans had long feared the news of her passing. In 2013, she first revealed that she had been diagnosed with brain cancer and had been told by her doctors she had as little as three months to live. Some responded as if a family member were in peril.

But she refused to despair. "I'm not dying until I do," Harper said in an interview on NBC's Today show. "I promise I won't." Harper did outlive her famous co-star: Mary Tyler Moore died in January 2017. Ed Asner, Cloris Leachman and Betty White are among the former cast members who survive her.

Harper and actor Ed Asner pose with their Emmy statuettes at the annual Primetime Emmy Awards presentation in Los Angeles in May 1971. (Associated Press)

In recent years, Harper's other appearances included American Dad!, The Simpsons and Two Broke Girls.

Harper was a chorus dancer on Broadway as a teen before moving into comedy and improv when, in 1970, she auditioned for the part of a Bronx-born Jewish girl who would be a neighbour and pal of Minneapolis news producer Mary Richards on a new sitcom for CBS.

It seemed a long shot for the young, unknown actress. As she recalled, "I'm not Jewish, not from New York, and I have a small, shiksa nose." And she had almost no TV experience.

But Harper, who arrived for her audition some 20 pounds overweight, may have clinched the role when she blurted out in admiration to the show's tall, slender star: "Look at you in white pants without a long jacket to cover your behind!"

It was exactly the sort of thing Rhoda would say to "Mar," as Harper recalled in her 2013 memoir, I, Rhoda. Harper was signed without a screen test.

Harper is seen promoting her book I, Rhoda at the McGowan Theater in Washington, DC, in April 2013. (Kris Connor/Getty Images)

Of course, if CBS had gotten its way, Rhoda might have been a very different character with a much different actress in place. As The Mary Tyler Moore Show was being developed, its producers were battling a four-point decree from the network, which insisted that the nation's TV viewers would not accept series characters who were (1) divorced, (2) from New York, (3) Jewish or (4) have mustaches.

The producers lost on having Mary Richards divorced — instead, she had been dumped by her long-time boyfriend — but with Rhoda they overrode the network on two other counts.

The show that resulted was a groundbreaking hit, with comically relatable Rhoda one big reason.

From left: Mary Tyler Moore Show cast members Harper, Mary Tyler Moore and Cloris Leachman are seen at a reception prior to the Academy of Television Arts & Sciences Hall of Fame induction ceremony in February 1999 in Los Angeles. (Rose Prouser/Reuters)

"Women really identified with Rhoda because her problems and fears were theirs," Harper theorized in her book. "Despite the fact that she was the butt of most of her own jokes, so to speak ... her confident swagger masked her insecurity. Rhoda never gave up."

Neither did Harper, who confronted her own insecurities with similar moxie.

"I was always a little overweight," she once told The Associated Press. "I'd say, 'Hello, I'm Valerie Harper and I'm overweight.' I'd say it quickly before they could ... I always got called chubby, my nose was too wide, my hair was too kinky."

But as The Mary Tyler Moore Show evolved, so did Rhoda. Rhoda trimmed down and glammed up, while never losing her comic step. The audience loved her more than ever.

Star of spinoff

A spinoff seemed inevitable. In 1974, Rhoda was dispatched from Minneapolis back home to New York City, where she was reunited with her parents and younger sister in a new sitcom that costarred Nancy Walker, Harold Gould and Julie Kavner.

She also met and fell in love with the hunky owner of a demolition firm.

The premiere of Rhoda that September was the week's top-rated show, getting a 42 per cent share of audience against competition including Monday Night Football on ABC. And a few weeks later, when Rhoda and her fiance, Joe, were wed in a one-hour special episode, more than 52 million people — half of the U.S. viewing audience — tuned in.

Valerie Harper passed away. She was a wonderful actress and brought me so much joy. She will be missed rip❤️ —@cyndilauper

But Rhoda couldn't maintain those comic or popular heights. A domesticated, lucky-in-love Rhoda wasn't a funny Rhoda. By the end of the third season, the writers had taken a desperate step: Rhoda divorced Joe. Thus had Rhoda (and Harper) defied a third CBS taboo.

The series ended in 1978 with Harper having played Rhoda for a total of nine seasons.

She had captured the character by studying her Italian stepmother. But Harper's own ethnicity — neither Jewish nor Italian — was summed up in a New York Times profile as "an exotic mixture of Spanish-English-Scotch-Irish-Welsh-French-Canadian."

Theatre, film success

And she was not a Gothamite. Born in Suffern, N.Y., into a family headed by a peripatetic sales executive, she spent her early years in Oregon, Michigan and California before settling in Jersey City, N.J.

By high school, she was taking dance lessons in Manhattan several times a week. By age 15, she was dancing specialty numbers at Radio City Music Hall. By 18, she was in the chorus of the Broadway musical Li'l Abner (then appeared in the film adaptation a year later). She also danced in the musicals Take Me Along (starring Jackie Gleason) and Wildcat (starring Lucille Ball).

She found comedy when she fell in with a group of Second City players from Chicago who had taken up residence in Greenwich Village. One of these improv players was Richard Schaal, whom she wed in 1964. (They divorced in 1978.)

Condolences to the family of Valerie Harper. Going to miss you Rhoda Morgenstern! 😢❌⭕️ —@WilliamShatner

Harper and Schaal moved to Los Angeles in 1968. Two years later, in a theater production, she was spotted by a casting agent for the role of Rhoda.

During The Mary Tyler Moore, Harper appeared in her first major film, the comedy Freebie and the Bean, and later was cast in Blame It on Rio and an adaptation of Neil Simon's play Chapter Two.

Legal battles

In 1986, she returned to series TV with a family sitcom called Valerie. While not matching her past critical successes, the show proved popular. But in the summer of 1987, Harper and her manager, Tony Cacciotti, whom she had married a few months earlier, were embroiled in a highly publicized feud with Lorimar Telepictures, the show's production company, and its network, NBC.

In a dispute over salary demands, Harper had refused to report for work, missing one episode. The episode was filmed without her. She was back on duty the following week, only to be abruptly dumped and replaced by actress Sandy Duncan. The show was renamed Valerie's Family and then The Hogan Family.

Meanwhile, lawsuits and countersuits flew. In September 1988, a jury decided that Harper was wrongfully fired. She was awarded $1.4 million US compensation plus profit participation in the show (which continued without Harper until 1991).

Harper and husband Tony Cacciotti are seen in Los Angeles after a jury decided in her favour against Lorimar Telepictures Corp. in a dispute that ended her role in the Valerie television series. (Nick Ut/Associated Press)

"I felt vindicated," Harper wrote in her memoir. "I had beaten Lorimar and reclaimed my reputation."

During the 1990s, Harper starred in a pair of short-lived sitcoms (one of which, City, was created by future Oscar-winner Paul Haggis) and made guest appearances on series including Melrose Place, Sex and the City and Desperate Housewives.

She reunited with Moore in a 2000 TV film, Mary and Rhoda. In 2013, there was an even grander reunion: Harper and Moore were back together along with fellow MTM alumnae Leachman, White and Georgia Engel to tape an episode of White's hit comedy, Hot in Cleveland. It was the ensemble's first acting job together in more than 30 years and during a news conference Harper cited a valuable lesson: The character of Rhoda, she said, pointing to Moore, "taught me to thank your lucky stars for a fabulous friend."