Who knows, maybe there was behind the scenes stuff going on that we don't know about but made her want to get away, no idea. And yeah, she could be the best of all Germans, so I don't think her move to the Czechs was very much based on not being able to make the German team (for example in the previous two teams she was quite clearly the third German behind Hermann and Lölling, Griebel only got a chance when Fernstädt didn't start and then was not very impressive).
Now I'm curious about something which I can't really find much about: Fernstädt was born in CZE, but when did she/her family go to Germany, any idea?