During the interwar period, Austrian school economists played a fundamental role in establishing marginalism as a central principle of economics. In those years, the role of Mises in Vienna was especially pivotal in building up economics as a science based on the notion of subjective utility within a free institutional framework. As is well known, Mises was surrounded by several colleagues and students who were members of his intellectual circle (Mises's Kreis). This paper sheds some light on the theoretical contribution of Martha Stephanie (Steffy) Braun (Browne), a neglected Austrian economist in Mises's circle. Embedded in the Viennese cultural milieu of the time and trained as an Austrian school economist, Braun originally helped develop, and sometimes anticipated, some pivotal aspects of the economic theory of the Austrian school. Her focus was mainly on monetary issues, the nature of economic policy, and economic education, especially for women.