She began her career as a stage actress, starring in a Broadway production of Neil Simon's The Gingerbread Lady (1970–1971), for which she won a Theatre World Award.

[2] In 1969, Ruymen appeared as a model at the Miami International Boat Show to promote Sungard sunscreen, covering half her face in it before spending time in the sun, demonstrating the product's efficacy at preventing sunburns.

[5] In 1970, she was cast as Polly Meara in a Broadway production of Neil Simon's The Gingerbread Lady opposite Maureen Stapleton, which ran between December 1970 and 1971.

[2] She was subsequently cast in the lead role of Paul Bartel's horror film Private Parts (1972), playing a young woman who uncovers dark secrets in a Los Angeles hotel operated by her aunt.

[9] Between 1976 and 1977, Ruymen had a lead role on the sitcom The McLean Stevenson Show, playing the daughter of a hardware store proprietor.