In 1955, she made her first stage appearance in Moss Hart’s Broadway stage hit, Anniversary Waltz. At the age of 15, she played the role of Dame Sybil Thorndyke’s granddaughter in the Broadway play The Potting Shed.

She started her film career in 1958 with the Disney’s film The Light in the Forest followed by Holiday for Lovers (1959). In 1959, Lynley was nominated for the Golden Globe Award for Most Promising Newcomer – Female. In 1960 she was again nominated for the Golden Globe Award for Most Promising Newcomer – Female for the film Blue Denim.

In 1960, she married publicist Michael Selsman. The marriage produced one child, Jill Selsman (a director of short films), and ended in divorce in 1964.

The decline in her career started in the late 1960s and ’70s. She did smaller roles, guest appearances and appeared in low-budget productions like The Maltese Bippy, Norwood, The Four Deuces, The Washington Affair and Bad Georgia Road. In 1992, she acted in a low-budget thriller Spirits, as a nun. She acted in Flypaper (1997) followed by the low-budget film Drowning on Dry Land (1999). Many of the low-budget movies she acted in during the later part of her career were direct-to-video.

In 2000, in an interview with the San Francisco Chronicle, Lynley discussed the difficulty faced by middle-aged actresses in finding roles. She predicted she’d have a comeback in old age, stating, “I don’t mean to sound conceited, but I am a very talented actress, and I have my head screwed on right.” And she added “I’m not going to drug clinics, I look good, and I’ve got all my marbles. So I really believe I’ll be back.”

In 2006, she appeared in a 30-minute film, Vic, co-written and directed by Sage Stallone, the late son of Sylvester Stallone.

Lynley died aged 77 of a heart attack on September 3, 2019, at her home in Pacific Palisades, California.