This icon is Rosa Luxemburg as a teenager. I wonder whether she ever read escapist young adult fiction? I wonder whether there were any books that could have been described as that, in German (or Polish) when she was a teen, in the 1870s or 1880s?

Don't know about Polish, but in German the answer is easy: E.T.A. Hoffmann. He practically invented that genre for the entire continent of Europe.