A good performer passes without difficulties from one role to another and he/she perfectly inhabits the character.
Emma is incredibly talented, she completely inhabits the characters she plays from the inside. Emma is so versatile, she is a comedienne and also a great dramatic actress, she can make you laugh or cry.
She can completely hide her personality during the performance, and become that person and behave the same way that person would!
She makes us believe she is going through whatever her character is going through and she is able to change voice and gestures according to her character (for instance P.L. Travers in “Saving Mr Banks” or Petra in “Last Christmas”). Acting as Petra she was so busy with her role and immersed in the part that during the rehearsal she talked to director and to other actors speaking like a real Croatian immigrant!
She has also accepted bad roles, as Vivienne Rook, a divisive character with negative attitudes but with adoring crowd following her name. Emma has given birth to a fascinating figure, a complex antihero with a strong personality that arouses admiration in people thanks to her overflowing populism. She brought into her character the worst populism, with rhetorical speeches and themes, without making a mockery of her or turning her into a caricature.
Emma is extremely believable in the part despite her being completely different in real life.