LOS ANGELES (REUTERS/WASHINGTON POST) - Fans were on Sunday mourning the death of Charmian Carr, remembered for her role as the rebellious daughter Liesl Von Trapp in the popular Academy Award-winning film The Sound Of Music.

Carr died aged 73 on Saturday of complications from a rare form of dementia in the Los Angeles suburb of Woodland Hills, Reuters reported her family as saying in a statement.

She played Liesl, the eldest of the seven children of stern widower and retired Austrian navy captain Georg Von Trapp, played by Christopher Plummer, now 86, in the 1965 musical starring Julie Andrews, 80.

Her romantic dance scene with screen boyfriend Rolfe in a gazebo during a thunderstorm while singing I Am Sixteen Going On Seventeen was considered one of the movie's most charming scenes.

The film, based on the Rogers & Hammerstein stage musical of the same name, won five Oscars including Best Picture.

On Twitter, Kym Karath, who played Gretl, the youngest of the Von Trapp children, wrote: "It is with infinite sadness that I share the tragic news that the precious & exquisite Charmian Carr, beautiful Liesl, has passed away."

"She has been like a sister throughout my life. Excruciating," Karath, now 58, wrote, posting a photo of herself and Carr.

Debbie Turner, 60, who played the sixth von Trapp child Marta, wrote: "So sad to lose my movie big sister, Charmian Carr. A beautiful woman, inside and out. Rest in Peace."

Ted Chapin, president of the Rodgers & Hammerstein organisation, said in a statement: "It's always sad when a member of the family passes away and in the case of the 'family' of the movie The Sound Of Music, it's especially sad when it is the first of the group to go."

Actor Seth MacFarlane echoed the sentiments of fans when he tweeted: "So very saddened to hear of the death of Charmian Carr. She leaves behind one of the most memorable performances in movie history."

Heart-broken fan Erin Ruberry wrote on Twitter: "Charmian Carr, you'll always be 16 going on 17 to me."

Born Charmian Anne Farnon in Chicago, she was in her early 20s when she auditioned for the role. She changed her last name at the suggestion of The Sound Of Music's director Robert Wise.

Carr was 21 when she was cast in the 1965 film that would immortalise her as a spirited teen who prances around a gazebo with her beau and adoringly harmonises to Edelweiss with her father.

Although she was the daughter of a vaudevillian actress and a bandleader, Carr had no previous acting experience and little musical training outside the church choir. She did, however, have a lovely voice, elegant elocution and glistening blue eyes.

Perhaps most importantly, she did not look her age - a principal selling point when a mutual acquaintance introduced her to director Wise, who by Carr's account had already rejected would-be Liesls including Mia Farrow and Patty Duke.

In the film, Andrews played Maria, the rebellious Catholic novice dispatched to the Von Trapps' Salzburg home as a governess on the eve of World War II. Based loosely on a true story, the original musical and film adaptation endeared the von Trapps to generations.

Of the children, Liesl, the eldest, is the one audiences come to know best. Carr's I Am Sixteen Going on Seventeen is a playful duet with her co-star Daniel Truhitte, who protectively assures her that he is "17 going on 18".

After leaping with Liesl around a gazebo, where they have taken shelter from the rain, Rolf steals a kiss and flees - leaving Liesl behind to let out an exuberant "Wheeee!"

Filming the scene, Carr skilfully concealed the pain from a sprained ankle: The wardrobe department had forgotten to put antiskid backing on her demure heels, and during one take of the dance she slid through the gazebo's glass window. The scene was one of several in which Carr was caught in the rain or drenched by a fall into a river during a jaunt with Maria.

She acquired a certain allure, especially as the film aged and audience singalong screenings invited parody. "I guess it turned on a lot of teenage boys," Carr once told the Vancouver Sun. "I never thought of Liesl as a sex symbol, but she was!"

After the success of the film, she had a chance to appear on Peyton Place but studio officials, fearful that the TV soap opera would sully Liesl's persona, forbade her to accept.

Her only other significant role was in Evening Primrose (1966), a TV film with music by Stephen Sondheim in which she played a young woman living in a department store.

"It was hard to have your first role as the high spot of your career," she once told the London Daily Telegraph. "I felt smothered by Liesl. She began to feel like my evil twin, the perfect one that everyone loved."

Her acting career ended, she told the Calgary Herald, when she married a man who "didn't want an actress for a wife". She later appeared in commercials and became an interior designer.

Her clients included Michael Jackson, who she said had a fixation on The Sound Of Music.

Born in Chicago, Carr grew up in California's San Fernando Valley. In The Sound Of Music, she told an Australian interviewer, "music brought the family together - but in my real life music has torn my family apart".

Her parents were separated, and she recalled her mother, an alcoholic, remarking that "Charmian hasn't got any talent. She's just lucky".

Carr was attending college, modelling and working in a doctor's office when she met Wise, who suggested that she change her surname to the shorter Carr. She did her own singing in The Sound Of Music, although a sister Darleen was among the singers who provided high notes for the actors.

Her marriage to Jay Brent ended in divorce. Survivors include two daughters and four grandchildren.

Carr said that in time she came to accept her identification with Liesl. She hosted Sound Of Music singalongs, wrote a memoir, Forever Liesl (2000) and released a book, Letters To Liesl (2001), both with co-author Jean Strauss, about missives sent to her by the movie's fans.

"When people look at me and see Liesl, I believe they are looking into a mirror," she wrote in her memoir. "If the film has touched them in some way, it is because it represents the world as they want it to be. If it makes them feel love or happiness or hope, it is because they have these feelings inside them."