Born Mary Lacy in Baltimore, she was the daughter of James J. Lacy, an iron foundry owner and state comptroller from 1947 to 1950, and the former Rose Daily.
She was raised on Oakenshaw Place and Fenchurch Road and was a 1945 Mount Saint Agnes High School graduate. She was the valedictorian and president of her class.
She entered the College of Notre Dame of Maryland and completed three years of study by June 1948, when she married John H. Fetting, a downtown Baltimore jewelry business owner. She later returned to her college and earned a bachelor's degree in drama in 1969.
Family members said she was not a part of the management of A.H. Fetting jewelers, but she occasionally modeled gems at charity fashion shows.
In 1974, after raising her family, she decided to go into counseling after reading about adult children of alcoholics. She earned a master's degree in mental health from the Johns Hopkins School of Medicine and became a licensed certified social worker. She wrote her thesis on the adolescent offspring of alcoholics.
She became a counselor at the Glass Mental Health Center in Pikesville, where she worked from 1972 to 1978. She then established a private practice in Towson and worked counseling couples, individuals, substance abusers and others. She was also on the faculty of the Sheppard Pratt Hospital Education Center.
"Mary Fetting brought to the consultation room her intelligence, warmth and empathy, combined with a very real and practical approach to human behavior," said Dr. Evelyn Marx, a close colleague. "In addition to her work with her patients, she shared her knowledge of the complexities of the human condition in the capacity of mentor to many Baltimore-area physicians and clinicians. We have lost an irreplaceable person."
In 2009, she was diagnosed with non-Hodgkins lymphoma and decided to close her practice.
"It took three weeks of her retirement for her to say, 'This is not going to work,'" said her son, Mark R. Fetting, Legg Mason chairman and chief executive officer. "She became a volunteer at the Franciscan Center."
Mrs. Fetting joined the emergency outreach center on West 23rd Street and worked three days a week until this past April.
"Coming here to the center was a godsend for her and for us as well," said Judy Dobson, the center's director of responsive services. "She had a way about her of getting to know her clients and their stories. She accepted the people who needed help at face value. She loved her clients, and they knew it."
Mrs. Fetting assisted people facing eviction from their homes or with utility cut-off notices. She also helped clients get their prescriptions.
"She advised young mothers who came in to read to their children," Ms. Dobson said. "She started bringing in children's books, then she started going to the Dollar Store and bought more books."
Mrs. Fetting, an avid reader, began involving family members in the collection of books for the center. Soon she and others got students at Bryn Mawr School to run a book drive.
She created a library for clients. Officials at the Franciscan Center have named the library for Mrs. Fetting and have established a memorial fund.
Mrs. Fetting ran the Lady Equitable Race and was later a fitness walker. She enjoyed literature, politics, movies and musicals. She spent time at Stone Harbor, N.J., and was a devotee of Sherwood Gardens, where she endowed a plot. Over the years, she also attended sporting or artistic events involving her father, brothers, children and grandchildren.
A memorial service will be held at 10:30 a.m. Monday at St. Ignatius Roman Catholic Church, 740 N. Calvert St.
In addition to her son, survivors include another son, Dr. John H. Fetting III of Baltimore; three daughters, Dr. Margaret Ann Fetting of Camarillo, Calif., M. Lacy Fetting of Shrewsbury, Pa., and R. Jean Fetting of Benton, Ark.; two brothers, James J. Lacy Jr. and Joseph J. Lacy, both of Baltimore; and 12 grandchildren. Her husband of 54 years died in 2002.