She was particularly known for her work in horror films,[4] notably Village of the Damned; Dracula, Prince of Darkness; Rasputin, the Mad Monk and Quatermass and the Pit.

[7] The same year, she went to Rome on holiday and met Italian comic actor Walter Chiari, who recognised her talent and suggested she change her name to that of his favourite poet, Shelley.

[12] Ryan Gilbey, in her obituary in The Guardian, praises Shelley's acting in the Hammer films, considering that she had "a grounded, rational quality that instantly conferred gravitas on whatever lunatic occurrences were unfolding around her.

"[5] In Dracula, Prince of Darkness she starred opposite Christopher Lee, portraying a virtuous woman who reveals to her friend that she has been turned into a vampire in a scene which Gilbey describes as having "traumatised and tantalised" viewers.

[5] In Village of the Damned – based on John Wyndham's science fiction novel, The Midwich Cuckoos – she gave a "heartbreaking" performance as one of the mothers of the alien children.

[2] In 2010, writer and actor Mark Gatiss interviewed Shelley about her career at Hammer for his BBC documentary series A History of Horror.

[13][14] While making the 1961 TV film, A Story of David, she met Hollywood star Jeff Chandler, and they began a relationship.