Bellamy was born on September 19, 1943, in Los Angeles, California. Her family had ties to the establishment of Early Virginia and her father, Victor "Vic" Bellamy, was a Juilliard graduate and opera singer who later became a local Western actor. She attended Southern Methodist University (SMU) from which she graduated with a fine arts masters degree in 1970. She began her career with her own puppet theatre in her native Los Angeles and later began working professionally on the stage. Some of her stage work consists of appearances in The House of Blue Leaves at the Pasadena Playhouse, The Skin of Our Teeth at the Old Globe Theatre in San Diego and the title role in Sister Mary Ignatius Explains It All for You at Theater Geo in Los Angeles, and the handicapped Mrs. Nichols in Dorothy Parker’s The Ladies of the Corridor at the Tamarind Theater. In 1986, the Los Angeles Times wrote that she became her character of a snake handler in Talking With... (1986). "This is not an Actress," they wrote, "this is a swamp woman holding a box with holes in it." She was praised in her role of Sister Mary in Sister Mary Ignatius Explains It All For You at Theatre Geo in 1994. The Los Angeles Times wrote, "When Bellamy is good, she is very, very good."

She died from cancer at her home in Valley Village, California, three months later on June 17, 2001, at the age of 57. A memorial Service was held for Bellamy on July 7, 2001, at the Court Theater in West Hollywood, California, and her cremains were scattered in the Pacific Ocean. Bellamy, in her own words, said of her health in a 1999 interview, "I had tried crying and being in a snit about blindness, but that was real boring. I've learned to live with it as best I can, and I feel very blessed that this has happened."