She served multiple terms on the Hannover city council, and also worked as a certified economy correspondent, a lecturer, a research assistant, and a property management executive.
[2] She worked from 1972 as correspondent for the foreign department of a wholesaler,[1] moving the following year to a position as research assistant of the Deutsche Gesellschaft für die Vereinten Nationen [de] (German society for the United Nations).
She was a member of the state board (Landesvorstand) there from 1994, and became president of the party district Hannover-Stadt in 1996, and also of the Hildesheim region in 2006.
[3][2] Winterstein was a member of the federal parliament, Mitglied des Deutschen Bundestages, from 2002 to 2013, where she served as party speaker for film politics, and as president of the workgroup for budget.
[4] She has worked in a freelance capacity in the field of politics advisory, for companies such as CargoBeamer from 2014 and Global Bridges from 2018.