Her scientific work focuses on analytics and conceptual developments in the field of gender- and diversity-conscious social education.
For many years, Fleßner was involved in social policy and the institutional anchoring of public toddler care and early childhood education (crèche and kindergarten).
In 1980 she earned her doctorate degree from that university, studying the development of public preschool education in rural areas in Germany from 1870 to 1924.
From 1985 to 1991, Fleßner was a member of the City Council of Oldenburg focusing on urban development planning and youth welfare policy, specifically public early childhood education (crèche and kindergarten).
[7] She is a board member of the Bertha Ramsauer Foundation in Oldenburg,[8] and a member of the Scientific Advisory Board of the Center for Women and Gender Studies (ZIF); the center is jointly supported by the University of Hildesheim and HAWK Hildesheim / Holzminden / Göttingen.