What was Deborah Kerr’s role in the film 'Quo Vadis'?

'Quo Vadis' (Latin for "Where are you going?") is a 1951 American epic film made by MGM in Technicolor. It was directed by Mervyn LeRoy and produced by Sam Zimbalist, from a screenplay by John Lee Mahin, S.N. Behrman and Sonya Levien, adapted from the novel 'Quo Vadis' (1896) by Henryk Sienkiewicz. The novel previously had been made into an Italian film Quo Vadis (1924). The film starred Robert Taylor, Deborah Kerr, Leo Genn, and Peter Ustinov.

Marcus Vinicius (Robert Taylor) is a Roman military commander and the legate of the XIV Gemina. Returning from the wars, he falls in love with Lygia (Deborah Kerr), a devout Christian, and as a result, finds himself increasingly drawn to her religion. Though she grew up Roman as the adopted daughter of Aulus Plautius (Felix Aylmer), a retired general, Lygia is technically a hostage of Rome. Marcus persuades Nero (Peter Ustinov) to give her to him as a reward for the services he has rendered. Lygia resents this arrangement, but nevertheless falls in love with Marcus.