She is best remembered for her role as the anarchist love interest of Malcolm McDowell's character in the film if.... (1968).
In one scene, which gained particular notice in British cinema of the period, she impersonated a tiger and had sexual intercourse with McDowell's character Mick Travis on the floor of a cafe, which with the later violence in the film led to an X rating, leading Paramount to later cut the sexual content from the film.
Her husband initially protested when he learned of the nature of the role, but he agreed to her acting in it once she explained the point of the film and the context.
[3] She found work on the stage in the 1970s, performing in George Etherege's comedy She Would If She Could for the Nuffield Theatre Company at Lancaster University in 1972.
Noonan played the brief role of Barberina in Dennis Potter's TV serial Casanova (1971);[4] her scene is repeated multiple times during the six episodes.