As a young woman, Muntz studied to teach school, but her interest in art led to her take lessons in painting technique from W.C. Forster of Hamilton, Ontario from 1873 to 1881. Starting in 1882, she began to take classes at the Ontario School of Art where she studied with Lucius Richard O'Brien, and later under George Agnew Reid. Encouraged, she traveled to Paris, France to study at the renowned Académie Colarossi where she was influenced by the impressionist style. On her return to Canada, she set up a studio in Toronto and became an Associate of the Royal College of Art (ARCA). She would later move to Montreal to continue her art career at 6 Beaver Hall Square.
She interrupted her career following the death of her sister in 1915, when she took responsibility for raising a number of her sister's 11 children. To better take care of the children she married her brother-in-law Charles W.B. Lyall and set a studio up in the attic of their home. She continued to devote whatever time she could find to painting, but she lived only a few more years and died in 1930 in Toronto.