Mary was born in Allegheny City and studied art at the Pennsylvania Academy of Fine Arts in Philadelphia. She journeyed to Italy and Spain to study the old masters. In Paris she associated with leaders of the Impressionist school and became the friend of Degas. The main theme of her paintings and prints is motherhood, showing mothers and children in their intimate moments. From her Paris studio she helped expand the Impressionist movement by advising her wealthy friends to buy this type of art.