Is Cate a Nazi in the film??

I'm not sure that it does go beyond survival. It may be overkill, but the Nazis probably did not provide a quota like "turn in 5 people and you can live." Lena was probably forced to keep turning in people because until her husband obtained power, there was nothing else to keep her out of the concentration camps except her continuing usefulness to the Nazis. If she did not turn in a new person every once in awhile, she probably would've been killed.

In reply to the original topic, it is not true that almost all Germans were Nazis. Some were, of course, but people were, as was preveiously stated, simply too afraid (or in some cases too self-involved) to speak out against Nazism. We have to remember, too, that the German economy was in terrible shape after WW1, partly because of all the money that the Allies demanded from Germany in the Treaty of Versailles. After WW1, most Germans were very poor, and then Hitler came along and promised to make things better economically. And if nothing else, he did improve the economy. By choosing not to oppose Hitler, poor non-jewish people were ensuring their own survival. Furthermore, under Hitler, schools started teaching children how to be good Nazis and how to inform on Jews and dissidents. It is hard to oppose the Nazis when you have been brainwashed from the earliest age to revere them. And anyone who spoke up publically was quickly arrested and imprisoned/sent to a concentration camp. There could be little real organization against Hitler (if you want to find a resistence group to join, how will you find it?) and no public resistence. Given the same circumstances, most people of any nationality would support, or at least not speak or act against, Nazism or Nazi policy. It is wasy to blame people who are remote from us in time or place for failing to act, but the truth is, almost every nation or ethnic group has some history of genocide. And under the right conditions, Hitler could have come to power in any country.

She was a Jew and what is called a "greifer". A Jewish person who hunted for and turned in other Jews to the Gestapo in order to stay alive herself. Stella Kubler known in Berlin as the Blonde Poison was a greifer who survived the war by turning in Jews. But she wasn't the only Jew who did this kind of work. There were a number of others, including Kubler's own husband Rolf Isakssohn. It seems that Lena's character was based on these greifer though not necessarily on Stella Kubler. Was she also a Nazi? Hard to say but she could have been during the war. It was sometimes difficult to know whether someone was a Nazi or not; mostly people did whatever was necessary to survive.