First thing that came to my mind was this is one of the grossest movie ive seen
But thinking deeply after finishing this movie actually changed my mind about it a bit
Erika wanted to be the dominant and wanted to have the posesion of everything around her as she was being controlled and oppressed by her mother and she took the nearest chance to control anyone who enters her life 
Shubert was an important key in this movie because it was not mentioned just to admire his classical music but it was a way for us the audience to understand erika’s character in a deep and complex way
Erike here used shubert as a shield to her response to any situation in her life mentally or physically she hated to see anyone loving shubert or trying to play his music because she views shubert as something sacred and intimate reflecting her inner struggles and complexity of her life 
When walter played a shuberts classic during the audition scene we see erika how she looks uncomfortable and was triggered though she was supposed to show a different reaction as he played this piece of music to draw her attention and love grow between them so Instead of showing love to walter she decided to vote against him though he played it perfectly by other means she doesn’t want anyone to have the same interest as her as we say nowadays because she sees that it threatens her sense of control and dominance 
Another scene where she puts the shards of glass in anna’s jacket at first i thought because she was jealous because maybe she thought there was an attraction between walter and anna but in deeper level it may be jealousy but combined with that anna was going to play shubert,her shubert and that walter will see anna as a talented pianist who plays shubert perfectly
Its really impressive and thinking about every single scene while she was training her students and never shutting up just giving instructions really explains how important shubert is to her and how she wants to control everything around her
Erika wanted to prove herself 
Seeing the last 5 minutes of this film broke my heart seeing her standing in the hall waiting for the others to get into their seats waiting her to play though she’s brutally was bruised the other day and tears in her eyes and how her mother was underestimating her infront of anna’s mother 
This was a great one i have too much to write about this movie and yet i cant put them into words(yes i know i wrote too much)