In it, she pinpointed repression as the principle defense mechanism, and argued that the ego was key in the resolution of conflict and tension. In focusing on ego functions, she distinguished her work from her father's by moving away from the traditional thinking around drive theory, thus establishing herself as pioneer and theorist in her own right. During this time she, along with lifelong friend and collaborator Dorothy Burlingham-Tiffany and Eva Rosenfeld, founded the Hietzing School. This school was their attempt to create a more holistic educational curriculum informed by psychoanalytic principles.