Few of her British-made films were memorable, but Kendall shone in all of them: "Doctor in the House" and "The Constant Husband" (both 1954), "Abdullah the Great" (1955) and "The Adventures of Quentin Durward" and "Simon and Laura" (both 1956). She was whisked off to MGM to add her sparkle to the Gene Kelly musical "Les Girls" (1957).
By this time, Kendall was diagnosed with myloid leukemia and given two years to live. Her fiance Rex Harrison never told her the prognosis, obtained a divorce from wife Lili Palmer and married Kendall in 1957. She cut back on her film work to accompany Harrison on his "My Fair Lady" and "Bell, Book and Candle" tours, appearing in only two more films, the arch society comedy "The Reluctant Debutante" (1958) and "Once More with Feeling" (1960). Harrison also directed her in a play, "The Bright One", in 1958. Kendall died at the London Clinic in 1959, while making plans to shoot a television show. She was 32 years old.