Mochary was born as Mary Veronica Kasser in Budapest in 1942 to Alexander and Elisabeth Kasser. Her father was the manager of the largest paper mill in Eastern Europe. The family left Hungary at the end of World War II, immigrating first to Mexico and then to the United States. They settled in Montclair, New Jersey when Mochary was nine years old. She attended Montclair State College High School, an experimental high school at Montclair State College (now Montclair State University). She graduated from Wellesley College in 1963 with a B.A. degree in economics and from the University of Chicago Law School in 1967 with a J.D. degree.
