Ethical guidelines may have been in place but psychoanalysis was still in it's infancy, the huge importance of transference/counter-transference had yet to be realised. I'm not saying what Jung did (or didn't) do was ok, just pointing out that it wasn't necessarily black and white. In fact, it's partly due to those early mistakes, that we know so much about transference (erotic or otherwise) and how to work with it, in a way that's beneficial to the patient.

Was Spielrein only happy when she was with Jung? I doubt it, she first met Jung when she was 19 and suffering from a severe breakdown. She quickly got better, graduated and became a very prominent psychoanalyst in her own right - her work influenced both Freud and Jung. She was a very intelligent, talented woman. It's a pity the film doesn't focus on that part a bit more. She also married, had 2 children and lived a life, until she (and her 2 daughters) were executed by the SS, when she was 57.

Perhaps I'm projecting my own anxieties but I'd like to think she was able to get over her erotic transference and enjoy other fulfilling relationships

The film was quite enjoyable though - once I got past Knightly's excessive gurning. Spanking and psychoanalysis, what's not to like?!