Born in Monterey, Minnesota, on June 25, 1909, Marcella was the fourth daughter and last of eight children in the Brouillard family. The family lived on a farm, and she spent her childhood days playing baseball and sharing other activities with her brothers and nephews near her own age. Her father died in 1924, and some time later her mother moved to Minneapolis, where Marcella finished her last year of high school. She took some business courses and then went to Texas to live with her brother Ralph. 

For two years she worked at an insurance company as secretary, and then returned to Minneapolis to be with her aged mother. A ruptured appendix brought bills to pay, and she began working in the home of Dr. Hart, the surgeon who had taken care of her. Mrs. Hart was a nurse and assisted her husband in his work. Marcella, along with the housework, took care of their three small children. She enjoyed the work.

Her mother, who was a professional seamstress, taught Marcella to sew. She also liked to do embroidery, to crochet and knit. On September 4, 1934, she became a postulant with the Benedictine Sisters of Perpetual Adoration at Clyde, being brought there by her spiritual director, Rev. George Keefe. She entered the novitiate on May 26, 1935. 

 Her first vows were professed August 29, 1936, when she received the name, Sister M. Louise. Final vows followed on August 31, 1941, with the privilege of being consecrated a virgin in Mundelein, on January 4, 1953.

At Clyde, where she remained seventeen years, she worked in the correspondence department, answering countless letters from among the many received each day by the community. On laundry days, she was privileged to iron altar cloths and albs or other special accessories for the Mass, because she could do them to perfection.

Sister M. Louise was assigned to Mundelein priory from February 1956 to October 1957, going from there to Kansas City. In Kansas City, she served as subprioress for two years, finishing the term begun by Sister Hilda Mary Simon (then known as Sr. M. Amadea). At the end of the term, she returned to Clyde and received the assignment of cleaning the resident chaplain’s house, and serving meals to the chaplains from 1959 to 1965. Many priests came to know her well, and she had a profound respect for the priesthood. 

When she returned to Mundelein in August 1965, she assisted in the altar bread department, looking over breads.  Parkinson's disease was diagnosed in 1967. She suffered from it for nineteen years, needing as time went on total care.

In January 8, 1977 she was taken to the St. Louis Health Care Center. Here she patiently allowed the nursing staff to care for her, never making a complaint. Her brothers, Raymond and Norbert and their wives visited and kept up correspondence even when she could no longer communicate with them. Father Louis, when visiting his parents, would come to see her and offer Mass at her bedside. Another nephew, Brother Francis, OSB of Collegeville, Minnesota also visited each year. The love and faithfulness of the family was a tribute to the love they had for Sister M. Louise.

Sister M. Louise had black eyes, and was beautiful not only in her face which always wore a smile, but in her inner spirit and self-giving love. Some people have the gift of being able to minister to others by what they say and do without even realizing it. Just being themselves, by their natural cheerfulness and generous spirit, they teach values and truths without words. Sister M. Louise Brouillard was this kind of person.

God called Sister Louise to Himself on April 2, 1986 about 8 o'clock in the evening, she was 76 years of age, and 49 years professed. At the Vigil service held for her, Sisters mentioned her composure under stress, her gracious manner, her humor, her faithfulness at adoration, and her many hours praying for the fidelity of priests.