First of all you must live the role without spoiling the words or making them commonplace. Shut yourself off and play whatever goes through your head. Imagine the following scene: Pishchik has proposed to Charlotta, now she is his bride... How will she behave? Or: Charlotta has been dismissed but finds other employment in a circus of a café-chantant. How does she do gymnastics or sing little songs? Do your hair in various ways and try to find in yourself things which remind you of Charlotta. You will be reduced to despair twenty times in your search but don't give up. Make this German woman you love so much speak Russian and observe how she pronounces words and what are the special characteristics of her speech. Remember to play Charlotta in a dramatic moment of her life. Try to make her weep sincerely over her life. Through such an image you will discover all the whole range of notes you need.