Thinking about the fever and hallucinating I just realised that Lilia didn't use a single word of English during the episode.
That is even more incredible, because on a normal day, she will do that all the time!
I think English is "taking over" in the sense that she speaks it with more and more people and her confidence is rising. She also seems to realise that we are living in an English-speaking place.
Lately, Lilia has engaged in conversations with people that we were talking to and whom she might not know. A handyman cam round to fix doors and she was listening to me speaking to him, then asked him "what are you doing?". I don't believe she did that before, at least I did not notice.
She also uses a lot of English words in German sentences (most of them 'correctly' adapted to the German form).
But tonight, when she was hotter then your average hard disk, she managed not to slip a single word of English in.