A blue-eyed blonde with a bubbly personality, aptly dubbed 'the Champagne Girl' by studio publicists, she was born Cynthia Robichaux, one of five siblings, in Hammond, Louisiana. Her father was Louis Robichaux. Her mother ran a dancing school in Pascagoula, Mississippi. Cynthia began dancing in public under her mum's tutelage at the age of five, occasionally taking part in entertaining American soldiers who were stationed in the area. During her school years, she switched to acting in amateur dramatics.

At the age of eleven, Cynthia performed on Ken Murray's 'Blackouts' variety show in Los Angeles. At that time, she began to adopt the name 'Cindy Robbins' as her stage moniker. Several years later, the acclaimed character actress Shirley Booth saw potential in her and picked Cynthia for a part in her 1954 Broadway show 'By the Beautiful Sea', set on early 1900s Coney Island. The play was a hit and ran for 270 performances. On the strength of this success, Booth took Cynthia back to California to be cast in the lead role of another play, 'The Vacant Lot', at the La Jolla Playhouse in San Diego. Soon after, Universal-International signed her under contract.

Cynthia made her screen debut as a Native American girl in the early western series Brave Eagle (1955). Credited as Cindy Robbins, she went on to play supporting roles in a few second features, including in I Was a Teenage Werewolf (1957), and one A-grader, the big budget melodrama This Earth Is Mine (1959), starring Rock Hudson. The studio publicity machine reinforced her 'champagne girl' image with fanzine articles about Cynthia using champagne as a supplement to shampoo. She was also said to own a champagne-coloured toy poodle named Chu-Chu. In interviews, Cynthia named her favorite activities as being tennis, riding, surfing and skin diving.

For all the hype, Cynthia never progressed beyond the status of starlet. She guest-starred in many TV sitcoms (The Adventures of Ozzie and Harriet (1952), Leave It to Beaver (1957), McHale's Navy (1962)), occasional westerns (Wagon Train (1957), Outlaws (1960), The Tall Man (1960)) and crime dramas (Dragnet (1951), Markham (1959), Tightrope (1959), Perry Mason (1957)). Her most popular role was as the star's eldest daughter (Carol Porter) in the comedy series The Tom Ewell Show (1960) (Cynthia, then 23, playing a 15 year-old). The main storyline revolved around a maladroit realtor, struggling to cope with life in a household dominated entirely by females.

Long after her retirement from screen acting, Cynthia penned several teleplays for a TV youth anthology series, for which she also received associate producer credit. She had a daughter (Kimberly Beck) by her first husband William Howard Beck. Her second husband was singer-songwriter Tommy Leonetti , with whom she resided in Sydney, Australia, for many years until his death in 1979. Her third husband (whose surname she adopted in her later credits) was the producer, director and writer Robert Chenault who died in 2009.