Conley was born on 24 October 1943 in Hatfield, England.
[2] Conley created the lead female role in Kenneth MacMillan's Valley of Shadows.
[3] She also created lead roles in Antony Tudor's Knight Errant (1968), Frederick Ashton's Creatures of Prometheus (1969), MacMillan's Manon (1974), and John Neumeier's Gustav Mahler's Fourth Symphony (1977).
[2] Conley danced Empress Elisabeth in the 1983 New York City premiere of MacMillan's Mayerling.
In her later career, she was a character artist with the Royal Ballet.