I read what others thought of this for one reason: trying to understand it while not having to watch it again. Cate Blanchett has long been one of my favorite actors. She melts into roles like butter on hot bread. In this role, she began constructing the character for us; her talent, intellect, knowledge, life, family. Then she goes about deconstructing it all. As each piece falls away, Lydia does not even appear to try to stop what she is doing to cause it even in light of the mental decompensation she experiences. Essentially, it's a study of narcissistic predatory behavior. There is no concern for the impact of such behavior on the targets of that behavior. Lydia's humanity is missing. I was struck by the statement, "I am Petra's father." Very telling, that, because of who she was talking to at the moment.
This film was not for entertainment. It was way too uncomfortable for that. No, this film made a statement and illustrated a process. It was educational.