She was born Scilla Gabellini, one of five siblings, in Rimini on the Adriatic coast. Scilla initially studied law at Oxford University, graduating with a doctorate. Her interest in pursuing a legal career waned quickly, however, since her next move was a return to Italy for acting classes at Rome's Accademia Nazionale d'Arte Drammatica. At the age of seventeen, the voluptuous, blue-eyed Scilla became a body double for Sophia Loren (to whom she bore more than a passing resemblance), notably in the classic Boy on a Dolphin (1957). Two years later, she underwent cosmetic surgery to look less like Sophia in order to forge her own screen image.

In 1963, Scilla featured on the cover of several magazines, including Playboy, the Milanese publication Le Ore and Parade (at the time, the most widely read weekly in the U.S.). Though she went on to command leads in a number of films during the 60s, Scilla tended to be typecast in roles which emphasized her physical attributes, rather than her acting ability. She appeared most often in genre films, anything from innocuous sex comedies (Genitori in blue-jeans (1960), Bel Ami 2000 oder Wie verführt man einen Playboy? (1966)) to swashbuckling costume dramas (La Venere dei pirati (1960)), and from spaghetti westerns (Johnny Golden Poker (1966)) to peplum spectacles (Death on the Arena (1962), The Revenge of Spartacus (1964)). After 1971, she was afforded more challenging and critically acclaimed roles as a star in Italian TV miniseries.

Eleven years after leaving the screen, Scilla attracted media attention as a result of the murder of her 87-year old landlord father Giuseppe, by a crazed tenant at his villa on the via Campi di Torre Flavia in Ladispoli.